JS_GetScopeChain

Obsolete since JavaScript 1.8.7
This feature is obsolete.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.

Retrieves the scope chain for the JavaScript code currently running in a given context.

JS_GetScopeChain has been removed in SpiderMonkey 1.8.7 with no identical replacement. When you only used this function to retrieve the scope chain's global, then you can use the function JS_GetGlobalForScopeChain.

Syntax

JSObject *
JS_GetScopeChain(JSContext *cx);
Name Type Description
cx JSContext * The context to query.

Description

JS_GetScopeChain returns the first JSObject on the scope chain for the JavaScript code currently running in the given context, cx.

The ECMAScript standard, ECMA 262-3 §10, describes execution contexts and scope chains. A scope chain is a sequence of objects whose properties are searched whenever a script or function refers to a variable. These objects represent the lexical scope of the currently executing statement or expression, not the call stack, so they include:

  • the variable objects of any enclosing functions or let statements or expressions, and any objects selected by enclosing with statements, in order from the most-nested scope outward;
  • lastly the global object against which the function was created.

Note that cx's current global object, as set by JS_SetGlobalObject, is not guaranteed to be on the scope chain. If the currently executing function was created in the scope of a different global object, then that object will be the last object in the current scope chain. If the context is currently executing a script, and not in any function, it's running in a scope that was passed to JS_ExecuteScript or a similar function by the application. This scope chain may or may not contain cx's current global object.

If any code is currently executing in cx, JS_GetScopeChain returns a pointer to the first JSObject on the current scope chain. Otherwise, if cx has a global object, JS_GetScopeChain returns that. Otherwise, an error is reported and JS_GetScopeChain returns NULL.

To walk the scope chain, use JS_GetParent.

See Also