Associative Arrays in JavaScript [StartupCTO]

Last Updated: 25 Jul 2023

|

Author: dordal

Page locked

This page is currently locked for editing by another user. You have to wait until this user finishes editing or the lock expires.

Currently locked by: 114.119.144.200
Lock expires at: Mar 14, 2026 11:37 AM (296 min)

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.

= Associative Arrays in JavaScript =

Unlike PHP (and many other languages), JavaScript doesn't support associative arrays. **Period.** It //does// support objects, which can be used somewhat like an associative array, but without a lot of the usual array goodness. It's an imperfect world, and it bugs me all the time, but it's just the way it is. 

In JS, you can set up an array like so:
<code javascript>
var myArray = new Array();
myArray[0] = 'David';
myArray[1] = 'Jones';
</code>

But you can't do:

<code javascript>
var myArray = new Array();
myArray['firstname'] = 'David';             // not possible in JS
myArray['lastname'] = 'Jones';              // not possible in JS
</code>

That's because JavaScript doesn't support the associative (e.g. '' 'firstname' '') index. It only a numerical index (e.g. ''[0]''). 

However, you can create an object and assign arbitrarily named properties to it:
<code javascript>
var myObject = new Object();
myObject.firstname = 'David';
myObject.lastname = 'Jones';
// alternately, use the shorthand syntax:
var myObject2 = {firstname: 'David', lastname: 'Jones'};
</code>

You can access properties of this object with either the dot (''myObject.firstname'') or array (''myObject['firstname']'') notation. You can iterate over all its properties with a for...in loop:
<code javascript>
for (var index in myObject) {
  document.write ('key: ' + index + '; value: ' + myObject[index] + ' ');
}
</code>

The only thing you //can't// do is use the array functions, such as ''join()'' and ''splice()''. Those only work on true Arrays, which were created with the Array constructor and have numerical indexes.

Page locked

About Me

Recent Changes

Get In Touch

Follow