window array in mathjax

Question

I'm trying to understand MathJax's api for a hack i'm writing. The first line of code is an anonymous function that has a window array. What is this "window array"? Here is the code:

(function (d) {
            var b = window[d];
//...
})('MathJax')

Please help me make sense of this.

Answer 1

That isn't an array; it's just the window object.

In JavaScript, there are two ways to access an object's properties: object.property and object['property'].

The first syntax only works when the property's name is a valid JavaScript identifier; the second works for any property name.

Here's a contrive demonstration that somewhat matches your code (try it on JSFiddle):

function lookThroughWindow(nameOfProperty) {
    alert(window[nameOfProperty]);
}

var propertyName = 'location';
lookThroughWindow(propertyName);

// The above just does this:
alert(window.location);