Invoking a Function with call() and apply()

call() and apply() are predefined JavaScript function methods. Both methods can be used to invoke a function, and both methods must have the owner object as first parameter.

function myFunction(a, b) {
    return a * b;
}
myObject = myFunction.call(myObject, 10, 2);     // Will return 20 

 

function myFunction(a, b) {
    return a * b;
}
myArray = [10, 2];
myObject = myFunction.apply(myObject, myArray);  // Will also return 20 

 

The only difference is that call() takes the function arguments separately, and apply() takes the function arguments in an array. In JavaScript strict mode, the first argument becomes the value of this in the invoked function, even if the argument is not an object.
In "non-strict" mode, if the value of the first argument is null or undefined, it is replaced with the global object.

With call() or apply() you can set the value of this, and invoke a function as a new method of an existing object.

 http://www.w3schools.com/js/js_function_invocation.asp