Obsolete since JavaScript 1.8.5
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
JSExtendedClass
is an extended version of JSClass
with additional hooks.
A C/C++ program can use a JSExtendedClass
with the JS_InitClass
and JS_NewObject
APIs to create objects that have custom methods and properties implemented in C/C++.
Syntax
struct JSExtendedClass { JSClass base; JSEqualityOp equality; JSObjectOp outerObject; JSObjectOp innerObject; JSIteratorOp iteratorObject;// Added in SpiderMonkey 1.8 JSObjectOp wrappedObject; // Added in SpiderMonkey 1.8 ...and additional reserved fields. };
Name | Type | Description |
---|---|---|
base |
JSClass |
The basic class information and callbacks for this class. This contains some required fields. |
equality |
JSEqualityOp |
Optional. Overrides the JavaScript == and != operators. |
outerObject |
JSObjectOp |
Optional. Return the current outer object. This is used to implement split objects. |
innerObject |
JSObjectOp |
Optional. Return the current inner object. This is used to implement split objects. |
iteratorObject |
JSIteratorOp |
Added in SpiderMonkey 1.8 Optional. Creates and returns a new iterator. |
wrappedObject |
JSObjectOp |
Added in SpiderMonkey 1.8 Optional. If non-null, an object of this class may serve as a wrapper for another object. Wrappers sometimes transparently behave like the object they wrap. For example, an object and its wrappers are all equal under === . |
Description
To implement a custom class that uses any of the JSExtendedClass
callbacks:
- Create a
JSExtendedClass
and populate both thebase
fields and the extended fields. - Ensure that the additional reserved fields at the end of the
JSExtendedClass
areNULL
.JSClass
andJSExtendedClass
structs should usually be global, and in this case the compiler automatically initializes these fields toNULL
. (This is a feature of the C and C++ languages.) Otherwise, usememset
. - Set the
JSCLASS_IS_EXTENDED
flag inmyExtendedClass.base.flags
. - Pass
&myExtendedClass.base
to functions likeJS_InitClass
orJS_NewObject
that require aJSClass *
.