JavaScript: The Definitive Guide, Fourth Edition

Name

Function.apply( ) — invoke a function as a method of an object

Availability

JavaScript 1.2; JScript 5.5; ECMAScript v3

Synopsis

                  function.apply(thisobj, args)

Arguments

thisobj

The object to which function is to be applied. In the body of the function, thisobj becomes the value of the this keyword.

args

An array of values to be passed as arguments to function.

Returns

Whatever value is returned by the invocation of function.

Throws

TypeError

If this method is invoked on an object that is not a function or if this method is invoked with an args argument that is not an array or an Arguments object.

Description

apply( ) invokes the specified function as if it were a method of thisobj, passing it the arguments contained in the args array. It returns the value returned by the function invocation. Within the body of the function, the this keyword refers to the thisobj object.

The args argument must be an array or an Arguments object. Use Function.call( ) instead if you want to specify the arguments to pass to the function individually instead of as array elements.

Example

// Apply the default Object.toString(  ) method to an object that
// overrides it with its own version of the method. Note no arguments.
Object.prototype.toString.apply(o);

// Invoke the Math.max(  ) method with apply to find the largest
// element in an array. Note that first argument doesn't matter
// in this case.
var data = [1,2,3,4,5,6,7,8];
Math.max.apply(null, data);

See Also

Function.call( )