What does this syntax mean in javascript

Question

;(function(Register, $, undefined) {

'use strict';

Register.Model = {
    Uid: ''
};

Register.Handler= {
    init: function() {
        Register.Model.Uid= $('body').data('uid');
    }
};

})(window.Register= window.Register|| {}, jQuery);

Hello, I'm new to javascript and JQuery, the last line of the code above really confuses me. Please help me understand that syntax. Any books that I can learn from please?

Answer 1

first look at this:

(function(){
   console.log("executed");
})();

the code defines a function then immediately execute it, you can also pass parameter into the function, for example:

(function(a,b){
    console.log(a+b);//should print 3
})(1,2);

Answer 2

There are many things worth mentioning in that code.

1) This is a definition of a function which is called immediatly afterwards

(function(r, $, undefined){
   // some stuff
})(window.Register= window.Register|| {}, jQuery);

2) Note that

window.Register= window.Register|| {}

is passed as a first argument. This means that window.Register is set to window.Register if it already exists (actually if it evaluates to boolean true, which is close enough) or to new object {} otherwise. Since = operator returns thing on the right side this entire syntax is a shortcut for:

if (!window.Register) {
    window.Register = {};
}
(function(r, $, undefined){
   // some stuff
})(window.Register, jQuery);

3) The function accepts 3 arguments, however 2 were passed. Therefore the last argument named undefined will be undefined (which is supposed to be a keyword but someone may override it).

4) As for this line

'use striction';

it's probably a mistake and it should be 'use strict'; . It tells interpreter to use more strict rules (helpful for avoiding for example accidental globals). Read this for more info:

What does "use strict" do in JavaScript, and what is the reasoning behind it?

5) The semicolon ; in front is used because JavaScript allows to write code without semicolon in most but not all cases. In order to avoid potential errors putting a semicolon in front is necessary (assuming there actually is something in front of that code).

Hope it helps.