This section describes features that apply most directly to Web browsers. Having said that, except where specified otherwise, the requirements defined in this section do apply to all user agents, whether they are Web browsers or not.
A
browsing
context
is
an
environment
in
which
Document
objects
are
presented
to
the
user.
A
tab
or
window
in
a
Web
browser
typically
contains
a
browsing
context
,
as
does
an
iframe
or
frame
s
in
a
frameset
.
A
browsing
context
has
a
corresponding
WindowProxy
object.
A
browsing
context
has
a
session
history
,
which
lists
the
Document
objects
that
the
browsing
context
has
presented,
is
presenting,
or
will
present.
A
browsing
context
's
active
document
is
its
WindowProxy
object's
[[Window]]
internal
slot
value's
associated
Document
.
A
Document
's
browsing
context
is
the
browsing
context
whose
session
history
contains
the
Document
,
if
any
such
browsing
context
exists
and
has
not
been
discarded
.
In
general,
there
is
a
1-to-1
mapping
from
the
Window
object
to
the
Document
object,
as
long
as
the
Document
object
has
a
browsing
context
.
There
are
two
is
one
exceptions.
First,
a
A
Window
can
be
reused
for
the
presentation
of
a
second
Document
in
the
same
browsing
context
,
such
that
the
mapping
is
then
1-to-2.
This
occurs
when
a
browsing
context
is
navigated
from
the
initial
about:blank
Document
to
another,
with
replacement
enabled
.
Second,
a
Document
can
end
up
being
reused
for
several
Window
objects
when
the
document.open(
type
,
replace
)
method
is
used,
such
that
the
mapping
is
then
many-to-1.
A
Document
does
not
necessarily
have
a
browsing
context
associated
with
it.
In
particular,
data
mining
tools
are
likely
to
never
instantiate
browsing
contexts.
A
Document
created
using
an
API
such
as
createDocument()
never
has
a
browsing
context
.
And
the
Document
originally
created
for
an
iframe
element,
which
has
since
been
removed
from
the
document
,
has
no
associated
browsing
context,
since
that
browsing
context
was
discarded
.
To
set
the
active
document
of
a
browsing
context
browsingContext
to
a
Document
object
document
,
optionally
with
a
Window
object
window
,
run
these
steps:
If
window
is
not
given,
let
Let
window
be
document
's
relevant
global
object
.
Per this standard document can be created before window , which does not make much sense. See issue #2688 .
Set
browsingContext
's
WindowProxy
object's
[[Window]]
internal
slot
value
to
window
.
Set
window
's
associated
Document
to
document
.
Set window 's relevant settings object 's execution ready flag .
A browsing context can have a creator browsing context , the browsing context that was responsible for its creation. If a browsing context has a parent browsing context , then that is its creator browsing context . Otherwise, if the browsing context has an opener browsing context , then that is its creator browsing context . Otherwise, the browsing context has no creator browsing context .
If a browsing context context has a creator browsing context creator , it also has the following properties. In what follows, let creator document be creator 's active document at the time context is created:
To create a new browsing context , optionally given noopener :
If noopener was not given, let it be false.
Let browsingContext be a new browsing context .
Let realm execution context be the result of creating a new JavaScript realm with the following customizations:
For
the
global
object,
create
a
new
Window
object.
For
the
global
this
binding,
use
browsingContext
's
WindowProxy
object.
Set up a window environment settings object with realm execution context , and let settingsObject be the result.
Let
document
be
a
new
Document
,
marked
as
an
HTML
document
in
quirks
mode
,
whose
content
type
is
"
text/html
",
and
which
is
both
ready
for
post-load
tasks
and
completely
loaded
immediately.
Ensure
that
document
has
a
single
child
html
node,
which
itself
has
two
empty
child
nodes:
a
head
element,
and
a
body
element.
Set the active document of browsingContext to document .
Set the origin of document :
If browsingContext has a creator browsing context , then the origin of document is the creator origin .
Otherwise, the origin of document is a unique opaque origin .
If browsingContext has a creator browsing context , then set document 's referrer to the serialization of creator URL .
If browsingContext has a creator browsing context , then set document 's referrer policy to the creator referrer policy .
Implement the sandboxing for document .
Execute the Initialize document’s Feature Policy algorithm on document . [FEATUREPOLICY]
Add document to browsingContext 's session history .
If
noopener
is
false,
browsingContext
is
a
top-level
browsing
context
,
and
creator
origin
is
same
origin
with
document
's
origin
,
then
copy
the
sessionStorage
storage
area
of
the
creator
origin
from
the
creator
browsing
context
into
browsingContext
's
set
of
session
storage
areas.
These
areas
must
be
considered
separate,
not
affecting
each
other
in
any
way.
Return browsingContext .
Certain
elements
(for
example,
iframe
elements)
can
instantiate
further
browsing
contexts
.
These
elements
are
called
browsing
context
containers
.
Each browsing context container has a nested browsing context , which is either a browsing context or null.
If a browsing context is the nested browsing context of a browsing context container , then the browsing context is said to be nested through the browsing context container 's node document .
A browsing context child is said to be a child browsing context of another browsing context parent , if all of the following conditions hold:
child is a nested browsing context of a browsing context container element
element is connected
element 's shadow-including root 's browsing context is parent
A browsing context child is then a document-tree child browsing context of parent if it is a child browsing context and its browsing context container is not just connected , but also in a document tree .
A browsing context child may have a parent browsing context . This is the unique browsing context that has child as a child browsing context , if any such browsing context exists. Otherwise, the browsing context has no parent browsing context .
A browsing context A is said to be an ancestor of a browsing context B if there exists a browsing context A' that is a child browsing context of A and that is itself an ancestor of B , or if the browsing context A is the parent browsing context of B .
A browsing context that is not a nested browsing context has no parent browsing context , and is the top-level browsing context of all the browsing contexts for which it is an ancestor browsing context .
The transitive closure of parent browsing contexts for a browsing context that is a nested browsing context gives the list of ancestor browsing contexts .
The
list
of
the
descendant
browsing
contexts
of
a
Document
d
is
the
(ordered)
list
returned
by
the
following
algorithm:
Let list be an empty list.
For
each
child
browsing
context
of
d
that
is
nested
through
an
element
that
is
in
the
Document
d
,
in
the
tree
order
of
the
elements
nesting
those
browsing
contexts
,
run
these
substeps:
Append that child browsing context to the list list .
Append the list of the descendant browsing contexts of the active document of that child browsing context to the list list .
Return the constructed list .
A
Document
is
said
to
be
fully
active
when
it
has
a
browsing
context
and
it
is
the
active
document
of
that
browsing
context
,
and
either
its
browsing
context
is
a
top-level
browsing
context
,
or
it
has
a
parent
browsing
context
and
the
Document
through
which
it
is
nested
is
itself
fully
active
.
Because
they
are
associated
with
an
element,
child
browsing
contexts
are
always
tied
to
a
specific
Document
in
their
parent
browsing
context
.
User
agents
must
not
allow
the
user
to
interact
with
child
browsing
contexts
of
elements
that
are
in
Document
s
that
are
not
themselves
fully
active
.
The
following
example
illustrates
the
differences
between
active
and
fully
active
Document
objects.
Here
a.html
is
loaded
into
a
browser
window,
b-1.html
starts
out
loaded
into
an
iframe
as
shown,
and
b-2.html
and
c.html
are
omitted
(they
can
simply
be
an
empty
document).
<!-- a.html --> <!DOCTYPE html> <html lang="en"> <title>Browsing context A</title> <iframe src="b-1.html"></iframe> <button onclick="frames[0].location.href = 'b-2.html'">Click me</button> <!-- b-1.html --> <!DOCTYPE html> <html lang="en"> <title>Browsing context B</title> <iframe src="c.html"></iframe>
At
this
point,
the
documents
given
by
a.html
,
b-1.html
,
and
c.html
are
all
the
active
documents
of
their
respective
browsing
contexts
.
They
are
also
all
fully
active
.
After
clicking
on
the
button
,
and
thus
loading
a
new
Document
from
b-2.html
into
browsing
context
B,
we
have
the
following
results:
The
a.html
Document
remains
both
the
active
document
of
browsing
context
A,
and
fully
active
.
The
b-1.html
Document
is
now
not
the
active
document
of
browsing
context
B.
As
such
it
is
also
not
fully
active
.
The
new
b-2.html
Document
is
now
the
active
document
of
browsing
context
B,
and
is
also
fully
active
.
The
c.html
Document
is
still
the
active
document
of
browsing
context
C.
However,
since
it
is
nested
through
the
b-1.html
Document
,
which
is
itself
not
fully
active
,
this
means
the
c.html
Document
is
now
not
fully
active
(even
though
it
is
active
).
For more explorations of the complexities involved here, especially as it impacts the session history , see A Model of Navigation History . [NAVMODEL]
A
browsing
context
that
is
a
nested
browsing
context
can
be
put
into
a
delaying
load
events
mode
.
This
is
used
when
it
is
navigated
,
to
delay
the
load
event
of
its
browsing
context
container
before
the
new
Document
is
created.
The
document
family
of
a
browsing
context
consists
of
the
union
of
all
the
Document
objects
in
that
browsing
context
's
session
history
and
the
document
families
of
all
those
Document
objects.
The
document
family
of
a
Document
object
consists
of
the
union
of
all
the
document
families
of
the
browsing
contexts
that
are
nested
through
the
Document
object.
The content document of a browsing context container container is the result of the following algorithm:
If container 's nested browsing context is null, then return null.
Let context be container 's nested browsing context .
Let document be context 's active document .
If document 's origin and the origin specified by the current settings object are not same origin-domain , then return null.
Return document .
top
Returns
the
WindowProxy
for
the
top-level
browsing
context
.
parent
Returns
the
WindowProxy
for
the
parent
browsing
context
.
frameElement
Returns
the
Element
for
the
browsing
context
container
.
Returns null if there isn't one, and in cross-origin situations.
The
top
IDL
attribute,
on
getting,
must
run
the
following
algorithm:
Let
windowProxy
be
this
Window
object's
WindowProxy
object.
If
there
is
no
browsing
context
with
windowProxy
as
its
WindowProxy
object,
then
return
null.
Let context be that browsing context .
If
context
is
a
top-level
browsing
context
,
then
return
context
's
WindowProxy
object.
Otherwise,
context
must
have
a
top-level
browsing
context
(i.e.
an
ancestor
browsing
context
with
no
parent
browsing
context
).
Return
that
top-level
browsing
context
's
WindowProxy
object.
The
parent
IDL
attribute,
on
getting,
must
run
the
following
algorithm:
Let
windowProxy
be
this
Window
object's
WindowProxy
object.
If
there
is
no
browsing
context
with
windowProxy
as
its
WindowProxy
object,
then
return
null.
Let context be that browsing context .
If
context
is
a
child
browsing
context
of
another
browsing
context
parent
,
then
return
parent
's
WindowProxy
object.
Otherwise,
context
must
be
a
top-level
browsing
context
.
Return
context
's
WindowProxy
object.
The
frameElement
IDL
attribute,
on
getting,
must
run
the
following
algorithm:
Let
windowProxy
be
this
Window
object's
WindowProxy
object.
If
there
is
no
browsing
context
with
windowProxy
as
its
WindowProxy
object,
then
return
null.
Let context be that browsing context .
If context is not a nested browsing context , then return null.
Let container be context 's browsing context container .
If container 's node document 's origin is not same origin-domain with the current settings object 's origin , then return null.
Return container .
An example of when these IDL attributes can return null is as follows:
<!DOCTYPE html>
<iframe></iframe>
<script>
"use strict";
const element = document.querySelector("iframe");
const iframeWindow = element.contentWindow;
element.remove();
console.assert(iframeWindow.top === null);
console.assert(iframeWindow.parent === null);
console.assert(iframeWindow.frameElement === null);
</script>
Here
the
browsing
context
corresponding
to
iframeWindow
was
discarded
when
element
was
removed
from
the
document.
It is possible to create new browsing contexts that are related to a top-level browsing context without being nested through an element. Such browsing contexts are called auxiliary browsing contexts . Auxiliary browsing contexts are always top-level browsing contexts .
An auxiliary browsing context has an opener browsing context , which is the browsing context from which the auxiliary browsing context was created.
An auxiliary browsing context can be disowned .
The
opener
attribute's
getter
must
run
these
steps:
If the current browsing context is disowned , then return null.
If the current browsing context has no opener browsing context , then return null.
Return
the
current
browsing
context
's
opener
browsing
context
's
WindowProxy
object.
The
opener
attribute's
setter,
must
run
these
steps:
If the given value is null, then disown the current browsing context and return.
Return
the
result
of
calling
OrdinaryDefineOwnProperty
(this
Window
object,
"
opener
",
{
[[Value]]:
the
given
value,
[[Writable]]:
true,
[[Enumerable]]:
true,
[[Configurable]]:
true
}).
Rethrow
any
exceptions.
If
a
browsing
context
is
disowned
,
its
window.opener
attribute
is
null.
That
prevents
scripts
in
the
browsing
context
from
changing
any
properties
of
its
opener
browsing
context
's
Window
object
(i.e.,
the
Window
object
from
which
the
browsing
context
was
created).
Otherwise,
if
a
browsing
context
is
not
disowned
,
then
scripts
in
that
browsing
context
can
use
window.opener
to
change
properties
of
its
opener
browsing
context
's
Window
object.
For
example,
a
script
running
in
the
browsing
context
can
change
the
value
of
window.opener.location
,
causing
the
opener
browsing
context
to
navigate
to
a
completely
different
document.
A browsing context A is familiar with a second browsing context B if one of the following conditions is true:
A browsing context A is allowed to navigate a second browsing context B if the following algorithm returns true:
If A is not the same browsing context as B , and A is not one of the ancestor browsing contexts of B , and B is not a top-level browsing context , and A 's active document 's active sandboxing flag set has its sandboxed navigation browsing context flag set, then return false.
Otherwise, if B is a top-level browsing context , and is one of the ancestor browsing contexts of A , then:
If this algorithm is triggered by user activation and A 's active document 's active sandboxing flag set has its sandboxed top-level navigation with user activation browsing context flag set, then return false.
Otherwise, if this algorithm is not triggered by user activation and A 's active document 's active sandboxing flag set has its sandboxed top-level navigation without user activation browsing context flag set, then return false.
Otherwise,
if
B
is
a
top-level
browsing
context
,
and
is
neither
A
nor
one
of
the
ancestor
browsing
contexts
of
A
,
and
A
's
Document
's
active
sandboxing
flag
set
has
its
sandboxed
navigation
browsing
context
flag
set,
and
A
is
not
the
one
permitted
sandboxed
navigator
of
B
,
then
return
false.
Return true.
An
element
has
a
browsing
context
scope
origin
if
its
Document
's
browsing
context
is
a
top-level
browsing
context
or
if
all
of
its
Document
's
ancestor
browsing
contexts
all
have
active
documents
whose
origin
are
the
same
origin
as
the
element's
node
document
's
origin
.
If
an
element
has
a
browsing
context
scope
origin
,
then
its
value
is
the
origin
of
the
element's
node
document
.
Each browsing context is defined as having a list of one or more directly reachable browsing contexts . These are:
The transitive closure of all the browsing contexts that are directly reachable browsing contexts forms a unit of related browsing contexts .
Each
unit
of
related
browsing
contexts
is
then
further
divided
into
the
smallest
number
of
groups
such
that
every
member
of
each
group
has
an
active
document
with
an
origin
that,
through
appropriate
manipulation
of
the
document.domain
attribute,
could
be
made
to
be
same
origin-domain
with
other
members
of
the
group,
but
could
not
be
made
the
same
as
members
of
any
other
group.
Each
such
group
is
a
unit
of
related
similar-origin
browsing
contexts
.
There is also at most one event loop per unit of related similar-origin browsing contexts (though several units of related similar-origin browsing contexts can have a shared event loop ).
Browsing contexts can have a browsing context name . Unless stated otherwise, it is the empty string.
A valid browsing context name is any string with at least one character that does not start with a U+005F LOW LINE character. (Names starting with an underscore are reserved for special keywords.)
A
valid
browsing
context
name
or
keyword
is
any
string
that
is
either
a
valid
browsing
context
name
or
that
is
an
ASCII
case-insensitive
match
for
one
of:
_blank
,
_self
,
_parent
,
or
_top
.
These
values
have
different
meanings
based
on
whether
the
page
is
sandboxed
or
not,
as
summarized
in
the
following
(non-normative)
table.
In
this
table,
"current"
means
the
browsing
context
that
the
link
or
script
is
in,
"parent"
means
the
parent
browsing
context
of
the
one
the
link
or
script
is
in,
"top"
means
the
top-level
browsing
context
of
the
one
the
link
or
script
is
in,
"new"
means
a
new
top-level
browsing
context
or
auxiliary
browsing
context
is
to
be
created,
subject
to
various
user
preferences
and
user
agent
policies,
"none"
means
that
nothing
will
happen,
and
"maybe
new"
means
the
same
as
"new"
if
the
"
allow-popups
"
keyword
is
also
specified
on
the
sandbox
attribute
(or
if
the
user
overrode
the
sandboxing),
and
the
same
as
"none"
otherwise.
Keyword | Ordinary effect |
Effect
in
an
iframe
with...
| |
---|---|---|---|
sandbox=""
|
sandbox="allow-top-navigation"
| ||
none specified, for links and form submissions | current | current | current |
empty string | current | current | current |
_blank
| new | maybe new | maybe new |
_self
| current | current | current |
_parent
if
there
isn't
a
parent
| current | current | current |
_parent
if
parent
is
also
top
| parent/top | none | parent/top |
_parent
if
there
is
one
and
it's
not
top
| parent | none | none |
_top
if
top
is
current
| current | current | current |
_top
if
top
is
not
current
| top | none | top |
name that doesn't exist | new | maybe new | maybe new |
name that exists and is a descendant | specified descendant | specified descendant | specified descendant |
name that exists and is current | current | current | current |
name that exists and is an ancestor that is top | specified ancestor | none | specified ancestor/top |
name that exists and is an ancestor that is not top | specified ancestor | none | none |
other name that exists with common top | specified | none | none |
name that exists with different top, if familiar and one permitted sandboxed navigator | specified | specified | specified |
name that exists with different top, if familiar but not one permitted sandboxed navigator | specified | none | none |
name that exists with different top, not familiar | new | maybe new | maybe new |
Most of the restrictions on sandboxed browsing contexts are applied by other algorithms, e.g. the navigation algorithm, not the rules for choosing a browsing context given below.
The rules for choosing a browsing context , given a browsing context name name , a browsing context current , and a boolean noopener are as follows:
Let chosen be null.
Let new be false.
If
name
is
the
empty
string
or
an
ASCII
case-insensitive
match
for
"
_self
",
then
set
chosen
to
current
.
If
name
is
an
ASCII
case-insensitive
match
for
"
_parent
",
then
set
chosen
to
current
's
parent
browsing
context
,
if
any,
and
current
otherwise.
If
name
is
an
ASCII
case-insensitive
match
for
"
_top
",
then
set
chosen
to
current
's
top-level
browsing
context
,
if
any,
and
current
otherwise.
If
name
is
not
an
ASCII
case-insensitive
match
for
"
_blank
"
and
there
exists
a
browsing
context
whose
name
is
the
same
as
name
,
and
current
is
familiar
with
that
browsing
context,
and
the
user
agent
determines
that
the
two
browsing
contexts
are
related
enough
that
it
is
ok
if
they
reach
each
other,
then
set
chosen
to
that
browsing
context.
If
there
are
multiple
matching
browsing
contexts,
the
user
agent
should
set
chosen
to
one
in
some
arbitrary
consistent
manner,
such
as
the
most
recently
opened,
most
recently
focused,
or
more
closely
related.
This will be made more precise in issue #1440 .
Otherwise, a new browsing context is being requested, and what happens depends on the user agent's configuration and abilities — it is determined by the rules given for the first applicable option from the following list:
The user agent may inform the user that a popup has been blocked.
The user agent may offer the user one of:
Set chosen to a new top-level browsing context given noopener , and set new to true.
Set chosen to an existing top-level browsing context .
If this case occurs, it means that an author has explicitly sandboxed the document that is trying to open a link.
If the user declines or the user agent doesn't offer the above, the variables remain unchanged.
Set
chosen
to
a
new
auxiliary
browsing
context
given
noopener
with
the
opener
browsing
context
being
current
,
and
set
new
to
true.
If
name
is
not
an
ASCII
case-insensitive
match
for
"
_blank
",
then
chosen
's
name
must
be
set
to
name
.
If the newly created browsing context is immediately navigated , then the navigation will be done with replacement enabled .
Set chosen to current .
Do nothing.
User agents are encouraged to provide a way for users to configure the user agent to always reuse current .
If new is true, then:
Let flagSet be current 's active document 's active sandboxing flag set .
If flagSet 's sandboxed navigation browsing context flag is set, then current must be set as chosen 's one permitted sandboxed navigator .
If flagSet 's sandbox propagates to auxiliary browsing contexts flag is set, then all the flags that are set in flagSet must be set in chosen 's popup sandboxing flag set .
Return chosen and new .
Window
,
WindowProxy
,
and
Location
objects
Although typically objects cannot be accessed across origins , the web platform would not be true to itself if it did not have some legacy exceptions to that rule that the web depends upon.
When perform a security check is invoked, with a platformObject , identifier , and type , run these steps:
If
platformObject
is
a
Window
or
Location
object,
then:
Repeat for each e that is an element of ! CrossOriginProperties ( platformObject ):
If SameValue ( e .[[Property]], identifier ) is true, then:
If
type
is
"
method
"
and
e
has
neither
[[NeedsGet]]
nor
[[NeedsSet]],
then
return.
Otherwise,
if
type
is
"
getter
"
and
e
.[[NeedsGet]]
is
true,
then
return.
Otherwise,
if
type
is
"
setter
"
and
e
.[[NeedsSet]]
is
true,
then
return.
If
!
IsPlatformObjectSameOrigin
(
platformObject
)
is
false,
then
throw
a
"
SecurityError
"
DOMException
.
Window
and
Location
objects
both
have
a
[[CrossOriginPropertyDescriptorMap]]
internal
slot,
whose
value
is
initially
an
empty
map.
The
[[CrossOriginPropertyDescriptorMap]]
internal
slot
contains
a
map
with
entries
whose
keys
are
(
currentGlobal
,
objectGlobal
,
propertyKey
)-tuples
and
values
are
property
descriptors,
as
a
memoization
of
what
is
visible
to
scripts
when
currentGlobal
inspects
a
Window
or
Location
object
from
objectGlobal
.
It
is
filled
lazily
by
CrossOriginGetOwnPropertyHelper
,
which
consults
it
on
future
lookups.
User agents should allow a value held in the map to be garbage collected along with its corresponding key when nothing holds a reference to any part of the value. That is, as long as garbage collection is not observable.
For
example,
with
const
href
=
Object.getOwnPropertyDescriptor(crossOriginLocation,
"href").set
the
value
and
its
corresponding
key
in
the
map
cannot
be
garbage
collected
as
that
would
be
observable.
User
agents
may
have
an
optimization
whereby
they
remove
key-value
pairs
from
the
map
when
document.domain
is
set.
This
is
not
observable
as
document.domain
cannot
revisit
an
earlier
value.
For
example,
setting
document.domain
to
"
example.com
"
on
www.example.com
means
user
agents
can
remove
all
key-value
pairs
from
the
map
where
part
of
the
key
is
www.example.com,
as
that
can
never
be
part
of
the
origin
again
and
therefore
the
corresponding
value
could
never
be
retrieved
from
the
map.
If
O
is
a
Location
object,
then
return
«
{
[[Property]]:
"
href
",
[[NeedsGet]]:
false,
[[NeedsSet]]:
true
},
{
[[Property]]:
"
replace
"
}
».
Let
crossOriginWindowProperties
be
«
{
[[Property]]:
"
window
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
self
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
location
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
true
},
{
[[Property]]:
"
close
"
},
{
[[Property]]:
"
closed
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
focus
"
},
{
[[Property]]:
"
blur
"
},
{
[[Property]]:
"
frames
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
length
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
top
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
opener
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
parent
",
[[NeedsGet]]:
true,
[[NeedsSet]]:
false
},
{
[[Property]]:
"
postMessage
"
}
».
Repeat for each e that is an element of O 's document-tree child browsing context name property set :
Add { [[Property]]: e , [[HideFromKeys]]: true } as the last element of crossOriginWindowProperties .
Return crossOriginWindowProperties .
Indexed
properties
do
not
need
to
be
safelisted
as
they
are
handled
directly
by
the
WindowProxy
object.
Return true if the current settings object 's origin is same origin-domain with O 's relevant settings object 's origin , and false otherwise.
If
this
abstract
operation
returns
undefined
and
there
is
no
custom
behavior,
the
caller
needs
to
throw
a
"
SecurityError
"
DOMException
.
Let crossOriginKey be a tuple consisting of the current settings object , O 's relevant settings object , and P .
Repeat for each e that is an element of ! CrossOriginProperties ( O ):
If SameValue ( e .[[Property]], P ) is true, then:
If the value of the [[CrossOriginPropertyDescriptorMap]] internal slot of O contains an entry whose key is crossOriginKey , then return that entry's value.
Let originalDesc be OrdinaryGetOwnProperty ( O , P ).
Let crossOriginDesc be undefined.
If e .[[NeedsGet]] and e .[[NeedsSet]] are absent, then:
Let value be originalDesc .[[Value]].
If ! IsCallable ( value ) is true, then set value to an anonymous built-in function, created in the current Realm Record , that performs the same steps as the IDL operation P on object O .
Set crossOriginDesc to PropertyDescriptor { [[Value]]: value , [[Enumerable]]: false, [[Writable]]: false, [[Configurable]]: true }.
Otherwise:
Let crossOriginGet be undefined.
If e .[[NeedsGet]] is true, then set crossOriginGet to an anonymous built-in function, created in the current Realm Record , that performs the same steps as the getter of the IDL attribute P on object O .
Let crossOriginSet be undefined.
If e .[[NeedsSet]] is true, then set crossOriginSet to an anonymous built-in function, created in the current Realm Record , that performs the same steps as the setter of the IDL attribute P on object O .
Set crossOriginDesc to PropertyDescriptor { [[Get]]: crossOriginGet , [[Set]]: crossOriginSet , [[Enumerable]]: false, [[Configurable]]: true }.
Create an entry in the value of the [[CrossOriginPropertyDescriptorMap]] internal slot of O with key crossOriginKey and value crossOriginDesc .
Return crossOriginDesc .
If
P
is
"
then
",
@@toStringTag
,
@@hasInstance
,
or
@@isConcatSpreadable
,
then
return
PropertyDescriptor
{
[[Value]]:
undefined,
[[Writable]]:
false,
[[Enumerable]]:
false,
[[Configurable]]:
true
}.
Return undefined.
The reason that the property descriptors produced here are configurable is to preserve the invariants of the essential internal methods required by the JavaScript specification. In particular, since the value of the property can change as a consequence of navigation, it is required that the property be configurable. (However, see tc39/ecma262 issue #672 and references to it elsewhere in this specification for cases where we are not able to preserve these invariants, for compatibility with existing Web content.) [JAVASCRIPT]
The reason the property descriptors are non-enumerable, despite this mismatching the same-origin behavior, is for compatibility with existing Web content. See issue #3183 for details.
Let desc be ? O .[[GetOwnProperty]]( P ).
Assert: desc is not undefined.
If ! IsDataDescriptor ( desc ) is true, then return desc .[[Value]].
Assert: IsAccessorDescriptor ( desc ) is true.
Let getter be desc .[[Get]].
If
getter
is
undefined,
then
throw
a
"
SecurityError
"
DOMException
.
Return ? Call ( getter , Receiver ).
Let desc be ? O .[[GetOwnProperty]]( P ).
Assert: desc is not undefined.
If desc .[[Set]] is present and its value is not undefined, then:
Perform ? Call ( setter , Receiver , « V »).
Return true.
Throw
a
"
SecurityError
"
DOMException
.
Let keys be a new empty List .
Repeat for each e that is an element of ! CrossOriginProperties ( O ):
If e .[[HideFromKeys]] is not true, append e .[[Property]] to keys .
If
keys
does
not
contain
"
then
",
then
append
"
then
"
to
keys
.
Return the concatenation of keys and « @@toStringTag , @@hasInstance , @@isConcatSpreadable ».