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JavaScript Creating Your Own Arbitrary Tasks

Posted by Tony Brackins
Tony Brackins
28,766 Points

Help with code

Anyone feel like breaking down what this code means exactly?

!function(root){
  "use strict";

  function Dice(sides) {
    this.sides = sides;
  }

  Dice.prototype.roll = function () {
    var randomNumber = Math.floor(Math.random() * this.sides) + 1;
    return randomNumber;
  }

  if (typeof module !== 'undefined' && module.exports) {
    module.exports = Dice;
  } else {
    root.Dice = Dice;
  }

}(this);

Particularly !function(root){}(this)

and the if statement with module and module.exports etc.

Thanks in advance.

1 Answer

Steven Parker
Steven Parker
231,198 Points
Steven Parker
Steven Parker
231,198 Points

Here's a breakdown of the lines in question:

!function(root){...}(this)

This is an immediately invoked function expression (IIFE, pronounced "iffy"). The exclamation point (!) is a way to insure that the JavaScript engine recognizes it as a complete expression and not just a a function definition (another way would be to enclose the whole thing in parentheses). The function is invoked passing the current context ("this") as the argument, which is then assigned to the parameter variable "root".

  if (typeof module !== 'undefined' && module.exports)

The first part of this test determines that "module" exists (is not undefined), and the second part determines that it has a property named "exports". Based on that test, the following lines either assign the Dice function to that property, or to a "Dice" property which is added to the current context ("root").

Tony Brackins
Tony Brackins
28,766 Points

gotcha. Thx Steven. The checking for module piece is still a little cloudy for me though I read that it's checking for NodeJS but I need to do some further learning perhaps more object oriented programming.