Calls a specified JS function.


JSBool JS_CallFunction(JSContext *cx, JSObject *obj,
    JSFunction *fun, uintN argc, jsval *argv, jsval *rval);
Name Type Description
cx JSContext * Pointer to a JS context from which to derive runtime information. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext.
obj JSObject * The "current" object on which the function operates; the object specified here is "this" when the function executes.
fun JSFunction * Pointer to the function to call. fun should be a native function or JSAPI-compiled function. See below.
argc uintN Number of arguments you are passing to the function.
argv jsval * Pointer to the array of argument values to pass to the function.
rval jsval * Out parameter. On success, *rval receives the return value from the function call.


JS_CallFunction calls a specified function, fun, on an object, obj. In terms of function execution, the object is treated as this.

In argc, indicate the number of arguments passed to the function. In argv, pass a pointer to the actual argument values to use. There should be one value for each argument you pass to the function; the number of arguments you pass may be different from the number of arguments defined for the function.

rval is a pointer to a variable that will hold the function's return value, if any, on successful function execution.

If the called function executes successfully, JS_CallFunction returns JS_TRUE. Otherwise it returns JS_FALSE, and rval is undefined.

Warning: Calling JS_CallFunction is safe only if the fun argument could be passed to JS_GetFunctionObject safely: that is, it is a function implemented by a JSNative or JSFastNative or the result of a call to JS_CompileFunction, JS_CompileUCFunction, JS_CompileFunctionForPrincipals, or JS_CompileUCFunctionForPrincipals. Passing any other JSFunction pointer can lead to a crash or worse.


To call a method of an object, use JS_CallFunctionName.

If you have a Function object, call it using JS_CallFunctionValue.

See also

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Contributors to this page: Piers, ethertank, trevorh, MMondor, Dria, Jorend
Last updated by: ethertank,