Question

arr[key] = value;

where key is a jQuery object and value is an array.

Answer 1

Associative arrays don’t really exist in JavaScript. However, you can achieve similar functionality using JavaScript objects:

// Create object
var myObject = {
    key: value,
    helloText: "Hello World!"
};

// Access object in some statement via:
myObject.helloText
// ...or:
myObject["helloText"]

To use an object as a key, you would have to do something like:

var a = {
    helloText: "Hello World!"
};

var b = {};
b[a] = "Testing";

alert(b[a]); // Returns "Testing" (at least, in Safari 4.0.4)

Using an object as a key sounds a bit weird, though. Are you sure you need to do this?

Update:

You can’t actually use an object as a key in JavaScript. The reason the above code appears to work is that, in the statement b[a] = "Testing";, JavaScript converts a to a string via a.toString(), which results in "[object Object]", and uses this string as the key. So our statement is actually b["[object Object]"] = "Testing"; and our alert statement is exactly the same as alert(b["[object Object]"]);.

Thanks to CMS for pointing this out in the comments!

Update 2:

Tim Down points out that his JavaScript library jshashtable allows you use an object as a key.