JS ExecuteScript

Execute a compiled script.


JSBool JS_ExecuteScript(JSContext *cx, JSObject *obj, JSObject *scriptObj, jsval *rval);
Name Type Description
cx JSContext * The context in which to execute the script. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext.
obj JSObject *

The scope in which to execute the script. In the simplest cases, this should just be the embedding's global object.

obj must not be an array, an E4X XML object, a With object, or a proxy.

In ECMAScript terms, the script is executed in a new execution context, but that context is not initialized quite as described in any of the three cases in ECMA 262-3 §10.2. Instead:

  • The scope chain is initialized to contain obj, followed by its parent, then its parent's parent, etc. until NULL is reached.
  • Variable initialization is performed. If the JSOPTION_VAROBJFIX option is in effect (recommended), then the last object in the scope chain is used as the variable object. Otherwise obj is used.
  • The this value is obj.
scriptObj JSObject * The compiled script to execute.
rval jsval * Out parameter. On success, *rval receives the value from the last executed expression statement processed in the script.


JS_ExecuteScript executes a previously-compiled script, scriptObj.

If the script executes successfully, *rval receives the value from the last executed expression statement processed in the script, and JS_ExecuteScript returns JS_TRUE. Otherwise it returns JS_FALSE, and the value left in *rval is unspecified.

The JSAPI User Guide contains example code using compiled scripts.

To execute a script that has not been compiled, use JS_EvaluateScript instead.

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 Last updated by: Jorend,