There are a few thoughts we have to take note about Javascript Associative Arrays:

• Arrays (which act as hash tables) have nothing to do with the built-in Array object. They simply rely on the fact that object.property is the same as object["property"]. This means that the length property is not used, nor do any Array methods (such as join) do anything.
• The way to iterate over the items in an associate array is to use the for (value in array) construct, allowing you to access each item’s value via array[value].

Initialize a Javascript Associative Array:

var animals = {"cat": 0,  "dog": 1, "mouse": 2, "cow": 3, "horse": 4, "pig": 5,
"duck": 6, "goat": 7, "sheep": 8, "lion": 9};

Here’s a short example of doing the For Each loop equivalent in JavaScript:

for( var animals in names )
{
alert( names[i] );
}