JavaScript: The Good Parts

Chapter 8. Methods

Though this be madness, yet there is method in 't.

—William Shakespeare, The Tragedy of Hamlet, Prince of Denmark

JavaScript includes a small set of standard methods that are available on the standard types.

Array

array.concat(item...)

The concat method produces a new array containing a shallow copy of this array with the items appended to it. If an item is an array, then each of its elements is appended individually. Also see array.push(item...) later in this chapter.

var a = ['a', 'b', 'c'];
var b = ['x', 'y', 'z'];
var c = a.concat(b, true);
// c is ['a', 'b', 'c', 'x', 'y', 'z', true]

array.join(separator)

The join method makes a string from an array . It does this by making a string of each of the array 's elements, and then concatenating them all together with a separator between them. The default separator is ','. To join without separation, use an empty string as the separator.

If you are assembling a string from a large number of pieces, it is usually faster to put the pieces into an array and join them than it is to concatenate the pieces with the + operator:

var a = ['a', 'b', 'c'];
a.push('d');
var c = a.join('');    // c is 'abcd';

array.pop( )

The pop and push methods make an array work like a stack. The pop method removes and returns the last element in this array . If the array is empty, it returns undefined.

var a = ['a', 'b', 'c'];
var c = a.pop(  );    // a is ['a', 'b'] & c is 'c'

pop can be implemented like this:

Array.method('pop', function ( ) { return this.splice(this.length ...