JS function definition : meaning of the last parentheses [duplicate]

Answer 1

Check out this question: What is this practice called in JavaScript?

Basically, the function will execute with the parameters you pass it. In this example, param will have the value of jQuery:

(function(param) {
    ....     
})(JQuery);

Answer 2

meaning of the last brakets

(function() {
    ....     
})();

The () in the end causes the code inside the function to be executed immediately.

(function(param) {
    ....     
})(JQuery);

The (JQuery) in the end causes the code inside the function to be executed immediately, passing JQuery as a parameter to it.

(function(chat, Friend) {
    ....     
})(chat, chat.module("friend"));

The (chat, chat.module("friend")) in the end causes the code inside the function to be executed immediately, passing chat and chat.module("friend") as parameters to it.

Answer 3

Suppose we had:

function add1 (x) {
    return x+1;
}

Then we might call add1(5) to get the value 6.

But with the brackets, rather than calling add1(5), we can replace it with (function (x) {return x+1;})(5). Basically this creates a function, and applies it to the value 5 immediately, whereas when we call add1(5), we are using a named/defined function.