What is ["null"] in javascript?

Question

I am migrating an asp code to .net. I came across the following code but not sure what is it doing.

var collection = {};
if (typeof(collection["null"]) != "undefined" && 
    typeof(collection["null"][id]) != "undefined")

Can any well tell that what does collection["null"] does? If possible, how to define it in .Net

Just to give an idea, I made closedMealArea as a List in .Net

Thanks in advance

Cheers, wildanjel

Answer 1

In JavaScript, collection["null"] returns the property with the name "null" that is owned by the object collection. collection.null is equivalent to collection["null"].

Answer 2

It's just an array item.

Answer 3

All the above are correct, in some way. Javascript uses two different ways of accessing properties/method on an object, or items in what is effectively its version of an associative array. As mentioned by Soubok, they are object['propOrMethodName'] and object.propOrMethodName. They are equivalent.

Even a standard Array, with integer indices, can have named properties/methods. Javascript really makes no distinction on the whole. What you can't do, though, is nonArrayObject[n] or arrayObject.n where n is an integer.

In the case of the question, though, collection is explicitly an object:

var collection = {};

An array, with integer indices, would be declared thus:

var collection = [];

As the latter statement tests collection["null"][n] (assuming n is again an integer), I'd say that collection is intended to have a series of properties, each of which is an Array. One of those properties is named "null".