JavaScript: The Definitive Guide, 6th Edition

Array Methods

ECMAScript 3 defines a number of useful array manipulation functions on Array.prototype, which means that they are available as methods of any array. These ECMAScript 3 methods are introduced in the subsections below. As usual, complete details can be found under Array in the core reference section. ECMAScript 5 adds new array iteration methods; those methods are covered in ECMAScript 5 Array Methods.

join()

The Array.join() method converts all the elements of an array to strings and concatenates them, returning the resulting string. You can specify an optional string that separates the elements in the resulting string. If no separator string is specified, a comma is used. For example, the following lines of code produce the string “1,2,3”:

var a = [1, 2, 3];     // Create a new array with these three elements
a.join();              // => "1,2,3"
a.join(" ");           // => "1 2 3"
a.join("");            // => "123"
var b = new Array(10); // An array of length 10 with no elements
b.join('-')            // => '---------': a string of 9 hyphens

The Array.join() method is the inverse of the String.split() method, which creates an array by breaking a string into pieces.

reverse()

The Array.reverse() method reverses the order of the elements of an array and returns the reversed array. It does this in place; in other words, it doesn’t create a new array with the elements rearranged but instead rearranges them in the already existing array. For example, the following code, which uses the reverse() and join() methods, produces ...