Last Updated: 25 Jul 2023

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Author: dordal

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front-end-tech:javascript:associative-arrays-in-javascript [May 12, 2008 08:49 AM]
dordal 		front-end-tech:javascript:associative-arrays-in-javascript [Jul 11, 2023 04:46 PM]
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 += 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.