Javascript Object from External file, program

Question

I am so confused about JavaScript's object system. I know that everything is considered Object in JavaScript but in this code of Esprima, I don't see any statement to declare this project to be accessed with esrpima like the following line: (https://github.com/ariya/esprima/blob/master/esprima.js)

var syntax = esprima.parse(text);

My question is how and where to define something like esprima.parse(text) in Javascript so that it can be exported as external package and be accessed with the object name. I know how to define object like Object = {a: "B"}; but can't find a way to figure this out. Please help me!

(function (root, factory) {
    'use strict';

    // Universal Module Definition (UMD) to support AMD, CommonJS/Node.js,
    // Rhino, and plain browser loading.
    if (typeof define === 'function' && define.amd) {
        define(['exports'], factory);
    } else if (typeof exports !== 'undefined') {
        factory(exports);
    } else {
        factory((root.esprima = {}));
    }
}(this, function (exports) {
    'use strict';

    var Token,
        TokenName,
 ...

Answer 1

That's because it doesn't. The variable name, esprima, comes from code that includes esprima. For example:

var esprima = require('esprima');
esprima.parse(text);

You could give the variable any other name:

var foo = require('esprima');
foo.parse(text);

All the the esprima.js file does is define an object which is exported. It does not dictate the name of the variable to which the object is assigned to eventually.

---

If the script is loaded in a browser, it actually does define esprima explicitly. You can see it in line 55:

 factory((root.esprima = {}));

This creates an object and assigns it to root.esprima. But it's also a function call, so the object is passed to factory, which is the function defined in 57, which accept a parameter exports. This is where the code assigns all the properties to.