The JavaScript Diaries: Part 12

By Lee Underwood



This week we look at what happens with multidimensional and associative arrays. As you look at these you will start to understand where you can use JavaScript when building your Web sites.

Multidimensional Arrays

This type of an array is similar to parallel arrays. In a multidimensional array, instead of creating two or more arrays in tandem as we did with the parallel array, we create an array with several levels or "dimensions." Remember our example of a spreadsheet with rows and columns? This time, however, we have a couple more columns.

Multidimensional array compared to a spreadsheet column
Multidimensional arrays can be created in different ways. Let's look at one of these method. First, we create the main array, which is similar to what we did with previous arrays.

var emailList = new Array();

Next, we create arrays for elements of the main array:

emailList[0] = new Array("President", "Paul Smith", "psmith@domain.com");
emailList[1] = new Array("Vice President", "Laura Stevens", "lstevens@domain.com");
emailList[2] = new Array("General Manager", "Mary Larsen", "mlarsen@domain.com");
emailList[3] = new Array("Sales Manager", "Bob Lark", "blark@domain.com");

In this script we created "sub arrays" or arrays from another level or "dimension." We used the name of the main array and gave it an index number (e.g., emailList[0]). Then we created a new instance of an array and gave it a value with three elements.

In order to access a single element, we need to use a double reference. For example, to get the e-mail address for the Vice President in our example above, access the third element "[2]" of the second element "[1]" of the array named emailList.

It would be written like this:

var vpEmail = emailList[1][2]
alert("The address is: "+ vpEmail)
  1. We declared a variable, named it emailList, and initialized it with a value of a new instance of an array.
  2. Next, we created an array for each of the elements within the original array. Each of the new arrays contained three elements.
  3. Then we declared a variable named vpEmail and initialized it with the value of the third element (lstevens@domain.com) of the second element "[1]" of the array named emailList.

You could also retrieve the information using something like:

var title = emailList[1][0]
var email = emailList[1][2]
alert("The e-mail address for the " + title +" is: " + email)

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