3.6 Combining Arrays

NN 4, IE 4

3.6.1 Problem

You want to blend two or more separate arrays into one larger array.

3.6.2 Solution

To join arrays together, use the concat( ) method of the array object, passing a reference to the other array as a parameter:

var comboArray = myArray.concat(anotherArray);

Arrays joined through the concat( ) method are not altered. Instead, the concat( ) method returns the combined array as a new value, which you can preserve in a separate variable. The base array (the one used to invoke the concat( ) method) comes first in the combined array.

For combining multiple arrays, pass the additional arrays as comma-delimited parameters to the concat( ) method:

var comboArray = myArray.concat(otherArray1, otherArray2, otherArray3);

The combined array has items in the same order as they appear in the comma-delimited arguments.

3.6.3 Discussion

The concat( ) method is not limited to tacking one array onto another. Comma-delimited parameters to the method can be any data type. A value of any data type other than an array becomes another entry in the main array�in the same sequence as the parameters. You can even combine arrays and other data types in the group of parameters passed to the method.

In addition to the concat( ) method, a quartet of array methods let you treat an array like a stack for tacking on and removing items from the front or backends of the array. The push( ) method lets you append one or more items to the end of an array; the corresponding pop( ) method removes the last item from the array and returns its value. You can perform the same operations at the beginning of the array with the unshift( ) (append) and shift( ) (remove) methods. All four of these methods are implemented in NN 4 or later and IE 5.5 or later for Windows.

3.6.4 See Also

Recipe 3.5 for sorting an array�something you may wish to do once you add to an array; Recipe 3.7 for dividing an array.