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I am new to nodejs and javascript and I tried to get an answer for this question but after investing plenty of time, I couldn't find an answer on the internet.
I now know what require and export are doing. I am analyzing some code and it has the following code line: 

var $ = global.jQuery = window.$ = require('jquery');

So here as I have understood the export object of 'jquery' is returned. As I have read from this thread, the code is equal to:

var $ = (global.jQuery = (window.$ = require('jquery')));

I hope that this is correct. If not, what is the code meaning? Then my question is, what is now var $ containing?

Code Pope
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4 Answers4

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In javascript you can make multiple value assignments in the same statement.

Multiple = get evaluated right to left. Thus in your example $ is jQuery which is what is imported from the require

Simple visual example:

var obj_1={};
var obj_2={};

// creates properties on both objects and assigns same value to all 3 variables
var someVar = obj_1.a = obj_2.b = 10; 

console.log('obj_1', obj_1)
console.log('obj_2', obj_2)
console.log('someVar', someVar)
charlietfl
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1

All three of $, global.jQuery and window.$ are set to the return value of require('jquery'). I'm not entirely sure what the reason is.

I have used this pattern when working with objects to set a property of an object and a short working variable at the same time, eg:

this.myMethod = function (value) {
  var n = this.someReallyLongPropertyName = value;
  // no way am I typing this.someReallyLongPropertyName again!
  if (n == 1) return n % n * n + n;
  return 0;
}
James
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1

var $ = global.jQuery = window.$ = require('jquery');

is equivalent to

window.$ = require('jquery');
global.jQuery = window.$;
var $ = global.jQuery;

This according to me is just syntactic sugar to let people people who consume jQuery, do so however they want ($, or jQuery or jQ etc.)

xadhix
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what does require('jquery') return

require('jquery') returns a new jquery object, exported by modules.export as you're already familiar with. As any Node module, you can assign this to whatever you like.

Don't be confused by the $, it's a valid variable name in JavaScript.

why multiple assignments

Syntactical, one-liner convenience, that's all.

  • window.$ is for compatibility with running in the browser
  • global.jQuery is two fold.
    • Having jQuery available is a great fallback for when $ is unavailable such as when running multiple versions of jQuery. I've found this to be fairly common in large projects due to compatibility differences with some 3rd party projects.
    • Since variables are usually locally scoped in Node by default, global has additional, reserved meaning to make the jQuery object available to other portions of code without require()ing it again.
  • $ is the most common usage in the API examples, so it's there for comfort, not necessity.
tresf
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