JavaScript: The Definitive Guide, Fourth Edition

Array Methods

In addition to the [] operator, arrays can be manipulated through various methods provided by the Array class. The following sections introduce these methods. Many of the methods were inspired in part by the Perl programming language; Perl programmers may find them comfortingly familiar. As usual, this is an overview only; complete details can be found in the core reference section of this book.

join( )

The Array.join( ) method converts all the elements of an array to strings and concatenates them. You can specify an optional string that is used to separate 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
var s = a.join(  );   // s == "1,2,3"

The following invocation specifies the optional separator to produce a slightly different result:

s = a.join(", ");   // s == "1, 2, 3"

Notice the space after the comma. The Array.join( ) method is the inverse of the String.split( ) method, which creates an array by breaking up 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 ...