apply().js

The apply() method calls a function with a given this value and arguments provided as an array (or an array-like object).

Note: While the syntax of this function is almost identical to that of call(), 
the fundamental difference is that call() accepts an argument list, while apply() accepts a single array of arguments.

Examples
Using apply to chain constructors

You can use apply to chain constructors for an object, similar to Java. In the following example we will create a global Function method called construct, which will enable you to use an array-like object with a constructor instead of an arguments list.

Function.prototype.construct = function (aArgs) {
  var oNew = Object.create(this.prototype);
  this.apply(oNew, aArgs);
  return oNew;
};


Note: The Object.create() method used above is relatively new. For an alternative method using closures, please consider the following alternative:

Function.prototype.construct = function(aArgs) {
  var fConstructor = this, fNewConstr = function() { fConstructor.apply(this, aArgs); };
  fNewConstr.prototype = fConstructor.prototype;
  return new fNewConstr();
};


function MyConstructor() {
  for (var nProp = 0; nProp < arguments.length; nProp++) {
    this['property' + nProp] = arguments[nProp];
  }
}

var myArray = [4, 'Hello world!', false];
var myInstance = MyConstructor.construct(myArray);

console.log(myInstance.property1);                // logs 'Hello world!'
console.log(myInstance instanceof MyConstructor); // logs 'true'
console.log(myInstance.constructor);              // logs 'MyConstructor'