can someone please explain what the difference is between these two functions?
(function(Engine, $, undefined) { //hidden from scope
//public function below
Engine.Init = function() {
console.log("IM PUBLIC");
}
//anonymous functions below
function Login() {
console.log("IM PRIVATE");
}
})( window.Engine = window.Engine || {}, jQuery );
Specifically, I'd like to know why Engine.Init() is available in the Console but Login isn't.
Init is a property of the Engine object that refers to a function.
You can access it like any other property.
Login is a local variable within the anonymous, "immediately invoked function expression" (IIFE); like other local variables, its name is only visible within the declaring function
Engine is global because of the parameters:
(window.Engine = window.Engine || {}, jQuery)
and available in the global namespace, if you did:
Engine.Login = function(){}
That would be available globally.
The function Login is only available inside the scope of the anonymous self executing function.
There is not really a difference between the functions themselves. The only difference is that the first function is assigned to a property of an object (Engine.init) defined in global scope (window.Engine), whereas the second function is defined locally inside the immediately invoked function expression (IIFE).
Here is a equivalent, but simpler example:
function foo() {
// 1
window.globalFunc = function() {
// global/public
}
// 2
function localFunc() {
// local/private
}
}
foo();
Because the first function is explicitly assigned to a global variable, it can be accessed outside of foo, after foo was executed. localFunc is not exported and hence local to foo, i.e. it cannot be accessed and doesn't exist outside of foo.
This thing
function(Engine, $, undefined) {
...
}
is actually a closure. So everything define inside that function is available only in that scope. When you do
Engine.Init = ...
You create a property which is attached to Engine object. In your case Engine is a global object, which means that you have an access to it via the console.
