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What is the purpose of a self executing function in javascript?

Please, can someone explain to me what does that mean in JS:

var obj = (function(){ 
   // code
})()

Thanks

Answer 1

It is an anonymous function that is immediately executed. It’s return value is assigned to obj. For example:

var obj = (function () {
    return 10;
}()); //Notice that calling parentheses can go inside or outside the others

console.log(obj); //10

They are often used to introduce a new scope so you don’t clutter the scope the code is executing in:

var obj = (function () {
    var something = 10; //Not available outside this anonymous function
    return something;
}());

console.log(obj); //10

Note that since this is a function expression, and not a function declaration, it should have a semi-colon after the closing curly brace.