Typescript namespace translation to Javascript

Question

For the give typescript, a class is defined within a module

module league{ export class Player { first_name: string; last_name: string; constructor(first_name: string, last_name: string){ this.first_name = first_name; this.last_name=last_name; } } }

and it is translated to javascript:

var league; (function (league) { var Player = (function () { function Player(first_name, last_name) { this.first_name = first_name; this.last_name = last_name; } return Player; })(); league.Player = Player; })(league || (league = {}));

the typescript code is easy to understand but being not so familiar with javascript, can anyone explain the logic behind the javascript it generated?

Look up "IIFE", and "module pattern".

elclanrs
– elclanrs

2014-03-17 09:26:30 +00:00
Commented Mar 17, 2014 at 9:26 — elclanrs
– elclanrs, Commented Mar 17, 2014 at 9:26

basarat · Accepted Answer · 2014-03-17 10:33:02Z

Module

Line by line explanation of module:

var league;

So that javascript doesn't throw an error that we are using an undefined variable.

(function (league) { }()

An immediately executing function. Required since scope is only created by functions in javascript.

league || (league = {}

So that the module can be slipt into multiple parts. If its already defined it is used, otherwise || we create it league = {}

I suppose that is what you were after. Classes are a seperate subject.

Class

Line by line. Again an immediately executing function to create a new scope (additionally it will help with inheritance, but not relevant here) :

var Player = (function () { })();

And the body is simply a function that uses this:

 function Player(first_name, last_name) { this.first_name = first_name; this.last_name = last_name; }

More

to learn more about immediately executing functions and this I recommend a javascript book. e.g. JavaScript good parts.

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