Status: Last call for comments
Status: Last call for comments
Various mechanisms can cause author-provided executable code to run in the context of a document. These mechanisms include, but are probably not limited to:
script
elements.javascript:
URLs (e.g. the src
attribute of img
elements, or an @import
rule in a CSS
style
element block).addEventListener()
, by explicit event handler
content attributes, by event handler IDL
attributes, or otherwise.Status: Last call for comments
Scripting is enabled in a browsing context when all of the following conditions are true:
Scripting is disabled in a browsing context when any of the above conditions are false (i.e. when scripting is not enabled).
Scripting is enabled for a
node if the Document
object of the node (the
node itself, if it is itself a Document
object) has an
associated browsing context, and scripting is enabled in that
browsing context.
Scripting is disabled for a node if there is no such browsing context, or if scripting is disabled in that browsing context.
Status: Last call for comments
Status: Last call for comments
A script has:
The characteristics of the script execution environment depend on the language, and are not defined by this specification.
In JavaScript, the script execution environment consists of the interpreter, the stack of execution contexts, the global code and function code and the Function objects resulting, and so forth.
Each code entry-point represents a block of executable code that the script exposes to other scripts and to the user agent.
Each Function object in a JavaScript script execution environment has a corresponding code entry-point, for instance.
The main program code of the script, if any, is the initial code entry-point. Typically, the code corresponding to this entry-point is executed immediately after the script is parsed.
In JavaScript, this corresponds to the execution context of the global code.
An object that provides the APIs that the code can use.
This is typically a Window
object. In JavaScript, this corresponds to the global
object.
When a script's global object is an empty object, it can't do anything that interacts with the environment.
If the script's global object is a
Window
object, then in JavaScript, the ThisBinding of
the global execution context for this script must be the
Window
object's WindowProxy
object,
rather than the global object. [ECMA262]
This is a willful violation of the
JavaScript specification current at the time of writing
(ECMAScript edition 5, as defined in section 10.4.1.1 Initial
Global Execution Context, step 3). The JavaScript specification
requires that the this
keyword in the global
scope return the global object, but this is not compatible with
the security design prevalent in implementations as specified
herein. [ECMA262]
A browsing context that is assigned responsibility for actions taken by the script.
When a script creates and navigates a new top-level browsing
context, the opener
attribute of the new browsing context's
Window
object will be set to the script's
browsing context's WindowProxy
object.
A Document
that is assigned responsibility for
actions taken by the script.
When a script fetches a resource, the current address of the
script's document will be used to set the Referer
(sic) header.
A character encoding, set when the script is created, used to encode URLs. If the character encoding is set from another source, e.g. a document's character encoding, then the script's URL character encoding must follow the source, so that if the source's changes, so does the script's.
A URL, set when the script is created, used to resolve relative URLs. If the base URL is set from another source, e.g. a document base URL, then the script's base URL must follow the source, so that if the source's changes, so does the script's.
Status: Last call for comments
When a user agent is to jump to a code entry-point for a script, for example to invoke an event listener defined in that script, the user agent must run the following steps:
If the script's global object is a
Window
object whose Document
object is
not fully active, then abort these steps without doing
anything. The callback is not fired.
Set the entry script to be the script being invoked.
Make the script execution environment for the script execute the code for the given code entry-point.
Set the entry script back to whatever it was when this algorithm started.
This algorithm is not invoked by one script calling another.
Status: Last call for comments
When the specification says that a script is to be created, given some script source, its scripting language, a global object, a browsing context, a URL character encoding, and a base URL, the user agent must run the following steps:
If scripting is disabled for browsing context passed to this algorithm, then abort these steps, as if the script did nothing but return void.
Set up a script execution environment as appropriate for the scripting language.
Parse/compile/initialize the source of the script using the script execution environment, as appropriate for the scripting language, and thus obtain the list of code entry-points for the script. If the semantics of the scripting language and the given source code are such that there is executable code to be immediately run, then the initial code entry-point is the entry-point for that code.
Set up the script's global object, the script's browsing context, the script's document, the script's URL character encoding, and the script's base URL from the settings passed to this algorithm.
Jump to the script's initial code entry-point.
When the user agent is to create an impotent script, given some script source, its scripting language, and a browsing context, the user agent must create a script, using the given script source and scripting language, using a new empty object as the global object, and using the given browsing context as the browsing context. The URL character encoding and base URL for the resulting script are not important as no APIs are exposed to the script.
When the specification says that a script is to be created from a node node, given some script source and its scripting language, the user agent must create a script, using the given script source and scripting language, and using the script settings determined from the node node.
The script settings determined from the node node are computed as follows:
Let document be the
Document
of node (or node itself if it is a
Document
).
The browsing context is the browsing context of document.
The global object is the Window
object of
document.
The URL character encoding is the character encoding of document. (This is a reference, not a copy.)
The base URL is the base URL of document. (This is a reference, not a copy.)
Status: Last call for comments
User agents may impose resource limitations on scripts, for
example CPU quotas, memory limits, total execution time limits, or
bandwidth limitations. When a script exceeds a limit, the user agent
may either throw a QUOTA_EXCEEDED_ERR
exception, abort
the script without an exception, prompt the user, or throttle script
execution.
For example, the following script never terminates. A user agent could, after waiting for a few seconds, prompt the user to either terminate the script or let it continue.
<script> while (true) { /* loop */ } </script>
User agents are encouraged to allow users to disable scripting
whenever the user is prompted either by a script (e.g. using the
window.alert()
API) or because of a
script's actions (e.g. because it has exceeded a time limit).
If scripting is disabled while a script is executing, the script should be terminated immediately.
Status: Last call for comments
Status: Last call for comments
To coordinate events, user interaction, scripts, rendering, networking, and so forth, user agents must use event loops as described in this section.
There must be at least one event loop per user agent, and at most one event loop per unit of related similar-origin browsing contexts.
An event loop always has at least one browsing context. If an event loop's browsing contexts all go away, then the event loop goes away as well. A browsing context always has an event loop coordinating its activities.
Other specifications can define new kinds of event loops that aren't associated with browsing contexts; in particular, the Web Workers specification does so.
An event loop has one or more task queues. A task queue is an ordered list of tasks, which can be:
Asynchronously dispatching an Event
object at a
particular EventTarget
object is a task.
Not all events are dispatched using the task queue, many are dispatched synchronously during other tasks.
The HTML parser tokenizing a single byte, and then processing any resulting tokens, is a task.
Calling a callback asynchronously is a task.
When an algorithm fetches a resource, if the fetching occurs asynchronously then the processing of the resource once some or all of the resource is available is a task.
Some elements have tasks that trigger in response to DOM manipulation, e.g. when that element is inserted into the document.
When a user agent is to queue a task, it must add the given task to one of the task queues of the relevant event loop. All the tasks from one particular task source (e.g. the callbacks generated by timers, the events dispatched for mouse movements, the tasks queued for the parser) must always be added to the same task queue, but tasks from different task sources may be placed in different task queues.
For example, a user agent could have one task queue for mouse and key events (the user interaction task source), and another for everything else. The user agent could then give keyboard and mouse events preference over other tasks three quarters of the time, keeping the interface responsive but not starving other task queues, and never processing events from any one task source out of order.
Each task that is queued onto a task queue of
an event loop defined by this specification is
associated with a Document
; if the task was queued in
the context of an element, then it is the element's
Document
; if the task was queued in the context of a
browsing context, then it is the browsing
context's active document at the time the task
was queued; if the task was queued by or for a script then the document is the
script's document.
A user agent is required to have one storage mutex. This mutex is used to control access to shared state like cookies. At any one point, the storage mutex is either free, or owned by a particular event loop or instance of the fetching algorithm.
Whenever a script calls into a plugin, and whenever a plugin calls into a script, the user agent must release the storage mutex.
Status: Last call for comments
An event loop must continually run through the following steps for as long as it exists:
Run the oldest task on one
of the event loop's task
queues, ignoring tasks whose associated
Document
s are not fully active. The user
agent may pick any task queue.
If the storage mutex is now owned by the event loop, release it so that it is once again free.
Remove that task from its task queue.
If any asynchronously-running algorithms are awaiting a stable state, then run their synchronous section and then resume running their asynchronous algorithm.
A synchronous section never mutates the DOM, runs any script, or has any other side-effects.
Steps in synchronous sections are marked with ⌛.
If necessary, update the rendering or user interface of any
Document
or browsing context to reflect
the current state.
Return to the first step of the event loop.
When an algorithm says to spin the event loop until a condition goal is met, the user agent must run the following steps:
Let task source be the task source of the currently running task.
Stop the currently running task, allowing the event loop to resume, but continue these steps asynchronously.
Wait until the condition goal is met.
Queue a task to continue running these steps, using the task source task source. Wait until this task runs before continuing these steps.
Return to the caller.
Some of the algorithms in this specification, for historical reasons, require the user agent to pause while running a task until some condition has been met. While a user agent has a paused task, the corresponding event loop must not run further tasks, and any script in the currently running task must block. User agents should remain responsive to user input while paused, however, albeit in a reduced capacity since the event loop will not be doing anything.
When a user agent is to obtain the storage mutex as part of running a task, it must run through the following steps:
If the storage mutex is already owned by this task's event loop, then abort these steps.
Otherwise, pause until the storage mutex can be taken by the event loop.
Take ownership of the storage mutex.
Status: Last call for comments
The following task sources are used by a number of mostly unrelated features in this and other specifications.
This task source is used for features that react to DOM manipulations, such as things that happen asynchronously when an element is inserted into the document.
This task source is used for features that react to user interaction, for example keyboard or mouse input.
Asynchronous events sent in response to user input (e.g. click events) must be dispatched using tasks queued with the user interaction task source. [DOMEVENTS]
This task source is used for features that trigger in response to network activity.
This task source is used to queue calls to history.back()
and similar
APIs.
javascript:
protocolStatus: Last call for comments
When a URL using the javascript:
protocol is dereferenced, the user agent must run
the following steps:
Let the script source be the string obtained using the
content retrieval operation defined for javascript:
URLs. [JSURL]
Use the appropriate step from the following list:
javascript:
URL, and the active document of that browsing
context has the same origin as the script given by
that URLLet address be the address of the active document of the browsing context being navigated.
If address is about:blank
,
and the browsing context being navigated has a
creator browsing context, then let address be the address of the creator
Document
instead.
Create a
script from the Document
node of the
active document, using the aforementioned script
source, and assuming the scripting language is JavaScript.
Let result be the return value of the initial code entry-point of this script. If an exception was raised, let result be void instead. (The result will be void also if scripting is disabled.)
When it comes time to set the document's address in the navigation algorithm, use address as the override URL.
Document
object of the element,
attribute, or style sheet from which the javascript:
URL was reached has an associated browsing
contextCreate an impotent script using the
aforementioned script source, with the scripting language set to
JavaScript, and with the Document
's object's
browsing context as the browsing context.
Let result be the return value of the initial code entry-point of this script. If an exception was raised, let result be void instead. (The result will be void also if scripting is disabled.)
Let result be void.
If the result of executing the script is void (there is no return value), then the URL must be treated in a manner equivalent to an HTTP resource with an HTTP 204 No Content response.
Otherwise, the URL must be treated in a manner equivalent to an
HTTP resource with a 200 OK response whose Content-Type metadata is
text/html
and whose response body is the return value
converted to a string value.
Certain contexts, in particular img
elements, ignore the Content-Type
metadata.
So for example a javascript:
URL for a
src
attribute of an
img
element would be evaluated in the context of an
empty object as soon as the attribute is set; it would then be
sniffed to determine the image type and decoded as an image.
A javascript:
URL in an href
attribute of an a
element would only be evaluated when the link was followed.
The src
attribute of an
iframe
element would be evaluated in the context of
the iframe
's own browsing context; once
evaluated, its return value (if it was not void) would replace that
browsing context's document, thus changing the
variables visible in that browsing context.
Status: Last call for comments
Status: Last call for comments
Many objects can have event handlers specified. These act as bubbling event listeners for the object on which they are specified.
An event handler can either
have the value null or be set to a Function
object. Initially, event handlers must be set to
null.
Event handlers are exposed in one or two ways.
The first way, common to all event handlers, is as an event handler IDL attribute.
The second way is as an event handler content attribute. Event handlers
on HTML elements and some of the event handlers on
Window
objects are exposed in this way.
Event handler IDL attributes, on setting, must set the corresponding event handler to their new value, and on getting, must return whatever the current value of the corresponding event handler is (possibly null).
If an event handler IDL attribute exposes an event handler of an object that doesn't exist, it must always return null on getting and must do nothing on setting.
This can happen in particular for event handler IDL attribute on
body
elements that do not have corresponding
Window
objects.
Certain event handler IDL attributes have additional
requirements, in particular the onmessage
attribute of
MessagePort
objects.
Event handler content attributes, when specified, must
contain valid JavaScript code matching the FunctionBody
production. [ECMA262]
When an event
handler content attribute is set, if the element is owned by
a Document
that is in a browsing context,
and scripting is enabled for
that browsing context, the user agent must run the
following steps to create a script after setting the content
attribute to its new value:
Set up a script execution environment for JavaScript.
Using this script execution environment, create a function object (as defined in ECMAScript edition 5 section 13.2 Creating Function Objects), with:
Document
, the
global environment).NewObjectEnvironment() is defined in ECMAScript edition 5 section 10.2.2.3 NewObjectEnvironment (O, E). [ECMA262]
Let this new function be the only entry in the script's list of code entry-points.
If the previous steps failed to compile the script, then set the corresponding event handler to null and abort these steps.
Set up the script's global object, the script's browsing context, the script's document, the script's URL character encoding, and the script's base URL from the script settings determined from the node on which the attribute is being set.
Set the corresponding event handler to the aforementioned function.
When an event handler content attribute is removed, the user agent must set the corresponding event handler to null.
When an event handler content attribute is set on an
element owned by a Document
that is not in a
browsing context, the corresponding event handler is
not changed.
All event handlers on an object, whether an element
or some other object, and whether set to null or to a
Function
object, must be registered as event listeners
on the object when it is created, as if the addEventListener()
method on the object's EventTarget
interface had been
invoked, with the event type (type
argument) equal to the type corresponding to the event handler (the
event handler event type), the listener set to be a
target and bubbling phase listener (useCapture argument set to
false), and the event listener itself (listener argument) set to do
nothing while the event handler's value is not a
Function
object, and set to invoke the call()
callback of the
Function
object associated with the event handler
otherwise.
Event handlers therefore always fire before event listeners
attached using addEventListener()
.
The listener argument is emphatically not the event handler itself.
The interfaces implemented by the event object do not influence whether an event handler is triggered or not.
When an event handler's
Function
object is invoked, its call()
callback must be invoked
with one argument, set to the Event
object of the event
in question.
The handler's return value must then be processed as follows:
mouseover
If the return value is a boolean with the value true, then the event must be canceled.
BeforeUnloadEvent
objectIf the return value is a string, and the event object's
returnValue
attribute's value is the empty string, then set the returnValue
attribute's value to the return value.
If the return value is a boolean with the value false, then the event must be canceled.
The Function
interface represents a function in the
scripting language being used. It is represented in IDL as
follows:
[Callback=FunctionOnly, NoInterfaceObject] interface Function { any call(in any... arguments); };
The call(...)
method is the object's callback.
In JavaScript, any Function
object implements this interface.
If the Function
object is a JavaScript Function
, then when it is invoked by the user agent,
the user agent must set the thisArg (as defined
by ECMAScript edition 5 section 10.4.3 Entering Function Code) to
the event handler's object. [ECMA262]
For example, the following document fragment:
<body onload="alert(this)" onclick="alert(this)">
...leads to an alert saying "[object Window]
" when the document is loaded,
and an alert saying "[object HTMLBodyElement]
" whenever the user
clicks something in the page.
The return value of the function is affects whether the event is
canceled or not: as described above, if
the return value is false, the event is canceled (except for mouseover
events, where the return
value has to be true to cancel the event). With beforeunload
events, the value is
instead used to determine the message to show the user.
Document
objects, and Window
objectsThe following are the event handlers (and their
corresponding event handler
event types) that must be supported by all HTML
elements, as both content attributes and IDL attributes, and
on Document
and Window
objects, as IDL
attributes.
Event handler | Event handler event type |
---|---|
onabort | abort
|
oncanplay | canplay
|
oncanplaythrough | canplaythrough
|
onchange | change
|
onclick | click
|
oncontextmenu | contextmenu
|
ondblclick | dblclick
|
ondrag | drag
|
ondragend | dragend
|
ondragenter | dragenter
|
ondragleave | dragleave
|
ondragover | dragover
|
ondragstart | dragstart
|
ondrop | drop
|
ondurationchange | durationchange
|
onemptied | emptied
|
onended | ended
|
onformchange | formchange
|
onforminput | forminput
|
oninput | input
|
oninvalid | invalid
|
onkeydown | keydown
|
onkeypress | keypress
|
onkeyup | keyup
|
onloadeddata | loadeddata
|
onloadedmetadata | loadedmetadata
|
onloadstart | loadstart
|
onmousedown | mousedown
|
onmousemove | mousemove
|
onmouseout | mouseout
|
onmouseover | mouseover
|
onmouseup | mouseup
|
onmousewheel | mousewheel
|
onpause | pause
|
onplay | play
|
onplaying | playing
|
onprogress | progress
|
onratechange | ratechange
|
onreadystatechange | readystatechange
|
onscroll | scroll
|
onseeked | seeked
|
onseeking | seeking
|
onselect | select
|
onshow | show
|
onstalled | stalled
|
onsubmit | submit
|
onsuspend | suspend
|
ontimeupdate | timeupdate
|
onvolumechange | volumechange
|
onwaiting | waiting
|
The following are the event handlers (and their
corresponding event handler
event types) that must be supported by all HTML
elements other than body
, as both content
attributes and IDL attributes, and on Document
objects,
as IDL attributes:
Event handler | Event handler event type |
---|---|
onblur | blur
|
onerror | error
|
onfocus | focus
|
onload | load
|
The following are the event handlers (and their
corresponding event handler
event types) that must be supported by Window
objects, as IDL attributes on the Window
object, and
with corresponding content attributes and IDL attributes exposed on
the body
and frameset
elements:
Event handler | Event handler event type |
---|---|
onafterprint | afterprint
|
onbeforeprint | beforeprint
|
onbeforeunload | beforeunload
|
onblur | blur
|
onerror | error
|
onfocus | focus
|
onhashchange | hashchange
|
onload | load
|
onmessage | message
|
onoffline | offline
|
ononline | online
|
onpagehide | pagehide
|
onpageshow | pageshow
|
onpopstate | popstate
|
onredo | redo
|
onresize | resize
|
onstorage | storage
|
onundo | undo
|
onunload | unload
|
The onerror
handler is also used for reporting script errors.
Status: Last call for comments
Certain operations and methods are defined as firing events on
elements. For example, the click()
method on the HTMLElement
interface is defined as
firing a click
event on the
element. [DOMEVENTS]
Firing a click
event means that a click
event, which bubbles and is
cancelable, and which uses the MouseEvent
interface,
must be dispatched at the given target. The event object must have
its screenX
, screenY
,
clientX
, clientY
, and
button
attributes set to 0, its ctrlKey
, shiftKey
, altKey
, and metaKey
attributes
set according to the current state of the key input device, if any
(false for any keys that are not available), its detail
attribute set to 1, and its relatedTarget
attribute set to null. The getModifierState()
method on the object must return
values appropriately describing the state of the key input device at
the time the event is created.
Firing a simple event named e means that an event with the name e, which does not bubble (except where otherwise
stated) and is not cancelable (except where otherwise stated), and
which uses the Event
interface, must be dispatched at
the given target.
The default action of these event is to do nothing except where otherwise stated.
Window
objectStatus: Last call for comments
When an event is dispatched at a DOM node in a
Document
in a browsing context, if the
event is not a load
event, the user
agent must also dispatch the event to the Window
, as
follows:
Window
object before propagating to any of the nodes,
as if the Window
object was the parent of the
Document
in the dispatch chain.Window
object at the end of the phase, unless bubbling
has been prevented, again as if the Window
object was
the parent of the Document
in the dispatch chain.Status: Last call for comments
This section only applies to user agents that support scripting in general and JavaScript in particular.
Whenever an uncaught runtime script error occurs in one of the
scripts associated with a Document
, the user agent must
report the error using the onerror
event handler of the script's global
object. If the error is still not handled after this, then
the error may be reported to the user.
When the user agent is required to report an error error using the event handler onerror, it must run these steps, after which the error is either handled or not handled:
Function
The function must be invoked with three arguments. The three
arguments passed to the function are all DOMString
s;
the first must give the message that the UA is considering
reporting, the second must give the absolute URL of
the resource in which the error occurred, and the third must give
the line number in that resource on which the error occurred.
If the function returns false, then the error is handled. Otherwise, the error is not handled.
Any uncaught exceptions thrown or errors caused by this function may be reported to the user immediately after the error that the function was called for; the report an error algorithm must not be used to handle exceptions thrown or errors caused by this function.
The error is not handled.
Status: Last call for comments
The setTimeout()
and setInterval()
methods allow authors to schedule timer-based callbacks.
[Supplemental, NoInterfaceObject] interface WindowTimers { long setTimeout(in any handler, in optional any timeout, in any... args); void clearTimeout(in long handle); long setInterval(in any handler, in optional any timeout, in any... args); void clearInterval(in long handle); }; Window implements WindowTimers;
setTimeout
( handler [, timeout [, arguments ] ] )Schedules a timeout to run handler after timeout milliseconds. Any arguments are passed straight through to the handler.
setTimeout
( code [, timeout ] )Schedules a timeout to compile and run code after timeout milliseconds.
clearTimeout
( handle )Cancels the timeout set with setTimeout()
identified by handle.
setInterval
( handler [, timeout [, arguments ] ] )Schedules a timeout to run handler every timeout milliseconds. Any arguments are passed straight through to the handler.
setInterval
( code [, timeout ] )Schedules a timeout to compile and run code every timeout milliseconds.
clearInterval
( handle )Cancels the timeout set with setInterval()
identified by handle.
This API does not guarantee that timers will fire exactly on schedule. Delays due to CPU load, other tasks, etc, are to be expected.
The WindowTimers
interface adds to the
Window
interface and the WorkerUtils
interface (part of Web Workers).
Each object that implements the WindowTimers
interface has a list of active timeouts and a list
of active intervals. Each entry in these lists is identified
by a number, which must be unique within its list for the lifetime
of the object that implements the WindowTimers
interface.
The setTimeout()
method must run the following steps:
Let handle be a user-agent-defined integer that is greater than zero that will identify the timeout to be set by this call.
Add an entry to the list of active timeouts for handle.
Get the timed task handle in the list of active timeouts, and let task be the result.
Get the timeout, and let timeout be the result.
If the currently running task is a task that was created by the
setTimeout()
method, and timeout is less than 4, then
increase timeout to 4.
Return handle, and then continue running this algorithm asynchronously.
If the method context is a Window
object, wait until the Document
associated with the
method context has been fully active for
a further timeout milliseconds (not
necessarily consecutively).
Otherwise, if the method context is a
WorkerUtils
object, wait until timeout milliseconds have passed with the worker
not suspended (not necessarily consecutively).
Otherwise, act as described in the specification that defines
that the WindowTimers
interface is implemented by
some other object.
Wait until any invocations of this algorithm started before this one whose timeout is equal to or less than this one's have completed.
The clearTimeout()
method must clear the entry identified as handle
from the list of active timeouts of the
WindowTimers
object on which the method was invoked,
where handle is the argument passed to the
method.
The setInterval()
method must run the following steps:
Let handle be a user-agent-defined integer that is greater than zero that will identify the interval to be set by this call.
Add an entry to the list of active intervals for handle.
Get the timed task handle in the list of active intervals, and let task be the result.
Get the timeout, and let timeout be the result.
If timeout is less than 10, then increase timeout to 10.
Return handle, and then continue running this algorithm asynchronously.
Wait: If the method context is a
Window
object, wait until the Document
associated with the method context has been fully
active for a further interval
milliseconds (not necessarily consecutively).
Otherwise, if the method context is a
WorkerUtils
object, wait until interval milliseconds have passed with the worker
not suspended (not necessarily consecutively).
Otherwise, act as described in the specification that defines
that the WindowTimers
interface is implemented by
some other object.
Return to the step labeled wait.
The clearInterval()
method must clear the entry identified as handle
from the list of active intervals of the
WindowTimers
object on which the method was invoked,
where handle is the argument passed to the
method.
The method context, when referenced by the algorithms
in this section, is the object on which the method for which the
algorithm is running is implemented (a Window
or
WorkerUtils
object).
When the above methods are invoked and try to get the timed task handle in list list, they must run the following steps:
If the first argument to the invoked method is an object that has an internal [[Call]] method, then return a task that checks if the entry for handle in list has been cleared, and if it has not, calls the aforementioned [[Call]] method with as its arguments the third and subsequent arguments to the invoked method (if any), and abort these steps.
Otherwise, continue with the remaining steps.
Apply the ToString() abstract operation to the first argument to the method, and let script source be the result. [ECMA262]
Let script language be JavaScript.
If the method context is a Window
object, let global object be the method
context, let browsing context be the
browsing context with which global
object is associated, let character
encoding be the character encoding of the Document
associated with global object (this is a reference, not a copy), and let
base URL be the base URL of the Document
associated with
global object (this is
a reference, not a copy).
Otherwise, if the method context is a
WorkerUtils
object, let global
object, browsing context, document, character encoding,
and base URL be the script's global
object, script's browsing context,
script's document, script's URL character
encoding, and script's base URL (respectively)
of the script that the
run a worker algorithm created when it created the
method context.
Otherwise, act as described in the specification that defines
that the WindowTimers
interface is implemented by
some other object.
Return a task that checks if the entry for handle in list has been cleared, and if it has not, creates a script using script source as the script source, scripting language as the scripting language, global object as the global object, browsing context as the browsing context, document as the document, character encoding as the URL character encoding, and base URL as the base URL.
When the above methods are to get the timeout, they must run the following steps:
Let timeout be the second argument to the method, or zero if the argument was omitted.
Apply the ToString() abstract operation to timeout, and let timeout be the result. [ECMA262]
Apply the ToNumber() abstract operation to timeout, and let timeout be the result. [ECMA262]
If timeout is an Infinity value, a Not-a-Number (NaN) value, or negative, let timeout be zero.
Round timeout down to the nearest integer, and let timeout be the result.
Return timeout.
The task source for these tasks is the timer task source.
Status: Last call for comments
Status: Last call for comments
alert
(message)Displays a modal alert with the given message, and waits for the user to dismiss it.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
confirm
(message)Displays a modal OK/Cancel prompt with the given message, waits for the user to dismiss it, and returns true if the user clicks OK and false if the user clicks Cancel.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
prompt
(message [, default] )Displays a modal text field prompt with the given message, waits for the user to dismiss it, and returns the value that the user entered. If the user cancels the prompt, then returns null instead. If the second argument is present, then the given value is used as a default.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
The alert(message)
method, when invoked, must
release the storage mutex and show the given message to the user. The user agent may make the
method wait for the user to acknowledge the message before
returning; if so, the user agent must pause while the
method is waiting.
The confirm(message)
method, when invoked, must
release the storage mutex and show the given message to the user, and ask the user to respond with
a positive or negative response. The user agent must then
pause as the method waits for the user's response. If
the user responds positively, the method must return true, and if
the user responds negatively, the method must return false.
The prompt(message, default)
method, when invoked, must release the storage mutex,
show the given message to the user, and ask the
user to either respond with a string value or abort. The user agent
must then pause as the method waits for the user's
response. The second argument is optional. If the second argument
(default) is present, then the response must be
defaulted to the value given by default. If the
user aborts, then the method must return null; otherwise, the method
must return the string that the user responded with.
Status: Last call for comments
print
()Prompts the user to print the page.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
The print()
method,
when invoked, must run the printing steps.
User agents should also run the printing steps whenever the user asks for the opportunity to obtain a physical form (e.g. printed copy), or the representation of a physical form (e.g. PDF copy), of a document.
The printing steps are as follows:
The user agent may display a message to the user and/or may abort these steps.
For instance, a kiosk browser could silently
ignore any invocations of the print()
method.
For instance, a browser on a mobile device could detect that there are no printers in the vicinity and display a message saying so before continuing to offer a "save to PDF" option.
The user agent must fire a simple event named
beforeprint
at the
Window
object of the Document
that is
being printed, as well as any nested browsing contexts in it.
The beforeprint
event can be used
to annotate the printed copy, for instance adding the time at
which the document was printed.
The user agent must release the storage mutex.
The user agent should offer the user the opportunity to obtain a physical form (or the representation of a physical form) of the document. The user agent may wait for the user to either accept or decline before returning; if so, the user agent must pause while the method is waiting. Even if the user agent doesn't wait at this point, the user agent must use the state of the relevant documents as they are at this point in the algorithm if and when it eventually creates the alternate form.
The user agent must fire a simple event named
afterprint
at the
Window
object of the Document
that is
being printed, as well as any nested browsing contexts in it.
The afterprint
event can be used
to revert annotations added in the earlier event, as well as
showing post-printing UI. For instance, if a page is walking the
user through the steps of applying for a home loan, the script
could automatically advance to the next step after having printed
a form or other.
Status: Last call for comments
showModalDialog
(url [, argument] )Prompts the user with the given page, waits for that page to close, and returns the return value.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
The showModalDialog(url, argument)
method, when invoked, must
cause the user agent to run the following steps:
Resolve url relative to the entry script's base URL.
If this fails, then throw a SYNTAX_ERR
exception
and abort these steps.
Release the storage mutex.
If the user agent is configured such that this invocation of
showModalDialog()
is
somehow disabled, then return the empty string and abort these
steps.
User agents are expected to disable this method in certain cases to avoid user annoyance (e.g. as part of their popup blocker feature). For instance, a user agent could require that a site be white-listed before enabling this method, or the user agent could be configured to only allow one modal dialog at a time.
Let the list of background browsing contexts be a list of all the browsing contexts that:
Window
object on which the showModalDialog()
method was
called, and thatshowModalDialog()
method at
the time the method was called,...as well as any browsing contexts that are nested inside any of the browsing contexts matching those conditions.
Disable the user interface for all the browsing contexts in the list of background browsing contexts. This should prevent the user from navigating those browsing contexts, causing events to be sent to those browsing context, or editing any content in those browsing contexts. However, it does not prevent those browsing contexts from receiving events from sources other than the user, from running scripts, from running animations, and so forth.
Create a new auxiliary browsing context, with the
opener browsing context being the browsing context of
the Window
object on which the showModalDialog()
method was
called. The new auxiliary browsing context has no name.
This browsing context's
Document
s' Window
objects all implement
the WindowModal
interface.
Let the dialog arguments of the new browsing context be set to the value of argument, or the 'undefined' value if the argument was omitted.
Let the dialog arguments' origin be the
origin of the script that called the showModalDialog()
method.
Navigate the new browsing context to the absolute URL that resulted from resolving url earlier, with replacement enabled, and with the browsing context of the script that invoked the method as the source browsing context.
Spin the event loop until the new browsing context is closed. (The user agent must allow the user to indicate that the browsing context is to be closed.)
Reenable the user interface for all the browsing contexts in the list of background browsing contexts.
Return the auxiliary browsing context's return value.
The Window
objects of Document
s hosted
by browsing contexts created
by the above algorithm must all have the WindowModal
interface added to their Window
interface:
[Supplemental, NoInterfaceObject] interface WindowModal { readonly attribute any dialogArguments; attribute DOMString returnValue; };
dialogArguments
Returns the argument argument that was
passed to the showModalDialog()
method.
returnValue
[ = value ]Returns the current return value for the window.
Can be set, to change the value that will be returned by the
showModalDialog()
method.
Such browsing contexts have associated dialog
arguments, which are stored along with the dialog
arguments' origin. These values are set by the showModalDialog()
method in the
algorithm above, when the browsing context is created, based on the
arguments provided to the method.
The dialogArguments
IDL attribute, on getting, must check whether its browsing context's
active document's origin is the same as the dialog arguments'
origin. If it is, then the browsing context's dialog
arguments must be returned unchanged. Otherwise, if the
dialog arguments are an object, then the empty string
must be returned, and if the dialog arguments are not
an object, then the stringification of the dialog
arguments must be returned.
These browsing contexts also have an associated return value. The return value of a browsing context must be initialized to the empty string when the browsing context is created.
The returnValue
IDL attribute, on getting, must return the return value
of its browsing context, and on setting, must set the return
value to the given new value.
The window.close()
method can be used to
close the browsing context.
Status: Last call for comments
The navigator
attribute of the Window
interface must return an
instance of the Navigator
interface, which represents
the identity and state of the user agent (the client), and allows
Web pages to register themselves as potential protocol and content
handlers:
interface Navigator { // objects implementing this interface also implement the interfaces given below }; Navigator implements NavigatorID; Navigator implements NavigatorOnLine; Navigator implements NavigatorAbilities; [Supplemental, NoInterfaceObject] interface NavigatorID { readonly attribute DOMString appName; readonly attribute DOMString appVersion; readonly attribute DOMString platform; readonly attribute DOMString userAgent; }; [Supplemental, NoInterfaceObject] interface NavigatorOnLine { readonly attribute boolean onLine; }; [Supplemental, NoInterfaceObject] interface NavigatorAbilities { // content handler registration void registerProtocolHandler(in DOMString scheme, in DOMString url, in DOMString title); void registerContentHandler(in DOMString mimeType, in DOMString url, in DOMString title); void yieldForStorageUpdates(); };
These interfaces are defined separately so that other
specifications can re-use parts of the Navigator
interface.
Status: Last call for comments
In certain cases, despite the best efforts of the entire industry, Web browsers have bugs and limitations that Web authors are forced to work around.
This section defines a collection of attributes that can be used to determine, from script, the kind of user agent in use, in order to work around these issues.
Client detection should always be limited to detecting known current versions; future versions and unknown versions should always be assumed to be fully compliant.
navigator
. appName
Returns the name of the browser.
navigator
. appVersion
Returns the version of the browser.
navigator
. platform
Returns the name of the platform.
navigator
. userAgent
Returns the complete User-Agent header.
appName
Must return either the string "Netscape
" or the full name of the browser, e.g. "Mellblom Browsernator
".
appVersion
Must return either the string "4.0
" or a string representing the version of the browser in detail, e.g. "1.0 (VMS; en-US) Mellblomenator/9000
".
platform
Must return either the empty string or a string representing the platform on which the browser is executing, e.g. "MacIntel
", "Win32
", "FreeBSD i386
", "WebTV OS
".
userAgent
Must return the string used for the value of the "User-Agent
" header in HTTP requests, or the empty string if no such header is ever sent.
Status: Last call for comments
The registerProtocolHandler()
method allows Web sites to register themselves as possible handlers
for particular schemes. For example, an online telephone messaging
service could register itself as a handler of the sms:
scheme ([RFC5724]), so that if the user
clicks on such a link, he is given the opportunity to use that Web
site. Analogously, the registerContentHandler()
method allows Web sites to register themselves as possible handlers
for content in a particular MIME type. For example, the
same online telephone messaging service could register itself as a
handler for text/directory
files ([RFC2425]), so that if the user has no
native application capable of handling vCards ([RFC2426]), his Web browser can instead
suggest he use that site to view contact information stored on
vCards that he opens.
navigator
. registerProtocolHandler
(scheme, url, title)navigator
. registerContentHandler
(mimeType, url, title)Registers a handler for the given scheme or content type, at the given URL, with the given title.
The string "%s
" in the URL is used as a
placeholder for where to put the URL of the content to be
handled.
Throws a SECURITY_ERR
exception if the user agent
blocks the registration (this might happen if trying to register
as a handler for "http", for instance).
Throws a SYNTAX_ERR
if the "%s
" string is missing in the URL.
User agents may, within the constraints described in this section, do whatever they like when the methods are called. A UA could, for instance, prompt the user and offer the user the opportunity to add the site to a shortlist of handlers, or make the handlers his default, or cancel the request. UAs could provide such a UI through modal UI or through a non-modal transient notification interface. UAs could also simply silently collect the information, providing it only when relevant to the user.
User agents should keep track of which sites have registered handlers (even if the user has declined such registrations) so that the user is not repeatedly prompted with the same request.
The arguments to the methods have the following meanings and corresponding implementation requirements:
registerProtocolHandler()
only)A scheme, such as ftp
or sms
. The
scheme must be compared in an ASCII case-insensitive
manner by user agents for the purposes of comparing with the
scheme part of URLs that they consider against the list of
registered handlers.
The scheme value, if it contains a colon
(as in "ftp:
"), will never match anything, since
schemes don't contain colons.
This feature is not intended to be used with non-standard protocols.
registerContentHandler()
only)A MIME type, such as
model/vnd.flatland.3dml
or
application/vnd.google-earth.kml+xml
. The MIME
type must be compared in an ASCII
case-insensitive manner by user agents for the purposes of
comparing with MIME types of documents that they consider against
the list of registered handlers.
User agents must compare the given values only to the MIME type/subtype parts of content types, not to the complete type including parameters. Thus, if mimeType values passed to this method include characters such as commas or whitespace, or include MIME parameters, then the handler being registered will never be used.
The type is compared to the MIME type used by the user agent after the sniffing algorithms have been applied.
A string used to build the URL of the page that will handle the requests.
When the user agent uses this URL, it must replace the first
occurrence of the exact literal string "%s
"
with an escaped version of the absolute URL of the
content in question (as defined below), then resolve the resulting URL, relative to the base URL of the entry
script at the time the registerContentHandler()
or registerProtocolHandler()
methods were invoked, and then navigate an
appropriate browsing context to the resulting URL
using the GET method (or
equivalent for non-HTTP URLs).
To get the escaped version of the absolute URL of the content in question, the user agent must replace every character in that absolute URL that doesn't match the <query> production defined in RFC 3986 by the percent-encoded form of that character. [RFC3986]
If the user had visited a site at http://example.com/
that made the following
call:
navigator.registerContentHandler('application/x-soup', 'soup?url=%s', 'SoupWeb™')
...and then, much later, while visiting http://www.example.net/
, clicked on a link such
as:
<a href="chickenkïwi.soup">Download our Chicken Kïwi soup!</a>
...then, assuming this chickenkïwi.soup
file
was served with the MIME type
application/x-soup
, the UA might navigate to the
following URL:
http://example.com/soup?url=http://www.example.net/chickenk%C3%AFwi.soup
This site could then fetch the chickenkïwi.soup
file and do whatever it is that it does with soup (synthesize it
and ship it to the user, or whatever).
A descriptive title of the handler, which the UA might use to remind the user what the site in question is.
User agents should raise SECURITY_ERR
exceptions if
the methods are called with scheme or mimeType values that the UA deems to be
"privileged". For example, a site attempting to register a handler
for http
URLs or text/html
content in a
Web browser would likely cause an exception to be raised.
User agents must raise a SYNTAX_ERR
exception if the
url argument passed to one of these methods does
not contain the exact literal string "%s
", or if resolving the url
argument with the first occurrence of the string "%s
" removed, relative to the entry
script's base URL, is
not successful.
User agents must not raise any other exceptions (other than binding-specific exceptions, such as for an incorrect number of arguments in an JavaScript implementation).
This section does not define how the pages registered by these methods are used, beyond the requirements on how to process the url value (see above). To some extent, the processing model for navigating across documents defines some cases where these methods are relevant, but in general UAs may use this information wherever they would otherwise consider handing content to native plugins or helper applications.
UAs must not use registered content handlers to handle content that was returned as part of a non-GET transaction (or rather, as part of any non-idempotent transaction), as the remote site would not be able to fetch the same data.
Status: Last call for comments
These mechanisms can introduce a number of concerns, in particular privacy concerns.
Hijacking all Web usage. User agents should not
allow schemes that are key to its normal operation, such as
http
or https
, to be rerouted through
third-party sites. This would allow a user's activities to be
trivially tracked, and would allow user information, even in secure
connections, to be collected.
Hijacking defaults. It is strongly recommended that user agents do not automatically change any defaults, as this could lead the user to send data to remote hosts that the user is not expecting. New handlers registering themselves should never automatically cause those sites to be used.
Registration spamming. User agents should
consider the possibility that a site will attempt to register a
large number of handlers, possibly from multiple domains (e.g. by
redirecting through a series of pages each on a different domain,
and each registering a handler for video/mpeg
—
analogous practices abusing other Web browser features have been
used by pornography Web sites for many years). User agents should
gracefully handle such hostile attempts, protecting the user.
Misleading titles. User agents should not rely
wholly on the title argument to the methods when
presenting the registered handlers to the user, since sites could
easily lie. For example, a site hostile.example.net
could claim that it was registering the "Cuddly Bear Happy Content
Handler". User agents should therefore use the handler's domain in
any UI along with any title.
Hostile handler metadata. User agents should protect against typical attacks against strings embedded in their interface, for example ensuring that markup or escape characters in such strings are not executed, that null bytes are properly handled, that over-long strings do not cause crashes or buffer overruns, and so forth.
Leaking Intranet URLs. The mechanism described in this section can result in secret Intranet URLs being leaked, in the following manner:
No actual confidential file data is leaked in this manner, but
the URLs themselves could contain confidential information. For
example, the URL could be
http://www.corp.example.com/upcoming-aquisitions/the-sample-company.egf
,
which might tell the third party that Example Corporation is
intending to merge with The Sample Company. Implementors might wish
to consider allowing administrators to disable this feature for
certain subdomains, content types, or schemes.
Leaking secure URLs. User agents should not send
HTTPS URLs to third-party sites registered as content handlers, in
the same way that user agents do not send Referer
(sic) HTTP headers from secure
sites to third-party sites.
Leaking credentials. User agents must never send username or password information in the URLs that are escaped and included sent to the handler sites. User agents may even avoid attempting to pass to Web-based handlers the URLs of resources that are known to require authentication to access, as such sites would be unable to access the resources in question without prompting the user for credentials themselves (a practice that would require the user to know whether to trust the third-party handler, a decision many users are unable to make or even understand).
Status: Last call for comments
This section is non-normative.
A simple implementation of this feature for a desktop Web browser might work as follows.
The registerContentHandler()
method could display a modal dialog box:
In this dialog box, "Kittens at work" is the title of the page
that invoked the method, "http://kittens.example.org/" is the URL of
that page, "application/x-meowmeow" is the string that was passed to
the registerContentHandler()
method as its first argument (mimeType),
"http://kittens.example.org/?show=%s" was the second argument (url), and "Kittens-at-work displayer" was the third
argument (title).
If the user clicks the Cancel button, then nothing further happens. If the user clicks the "Trust" button, then the handler is remembered.
When the user then attempts to fetch a URL that uses the "application/x-meowmeow" MIME type, then it might display a dialog as follows:
In this dialog, the third option is the one that was primed by the site registering itself earlier.
If the user does select that option, then the browser, in accordance with the requirements described in the previous two sections, will redirect the user to "http://kittens.example.org/?show=data%3Aapplication/x-meowmeow;base64,S2l0dGVucyBhcmUgdGhlIGN1dGVzdCE%253D".
The registerProtocolHandler()
method would work equivalently, but for schemes instead of unknown
content types.
Status: Last call for comments
navigator
. yieldForStorageUpdates
()If a script uses the document.cookie
API, or the
localStorage
API, the
browser will block other scripts from accessing cookies or storage
until the first script finishes.
[WEBSTORAGE]
Calling the navigator.yieldForStorageUpdates()
method tells the user agent to unblock any other scripts that may
be blocked, even though the script hasn't returned.
Values of cookies and items in the Storage
objects
of localStorage
attributes
can change after calling this method, whence its name.
[WEBSTORAGE]
The yieldForStorageUpdates()
method, when invoked, must, if the storage mutex is
owned by the event loop of the task that resulted in the method being
called, release the storage mutex so that it is once
again free. Otherwise, it must do nothing.