JavaScript function evaluating itself and calling itself at the same time

Question

I am learning about JavaScript functions on MDN

I came across an example that looks similar to this:

var saySomething = ( function(){console.log("hello")} )();

I have also seen this in the jQuery source.

I have not found any explanation of this style of function calling/definition on the MDN function reference.

I know from running the code that it calls itself immediately upon interpretation by the JavaScript engine.

Is this the Grouping Operator in action? Where it says:

So i was right on what I thought was going on with the grouping operator — Robert Rocha, Mar 10 '15 at 01:45

score 2 · Accepted Answer · answered Mar 10 '15 at 01:42

Google "Immediately Invoked Function Expression" or "IIFE".

The general syntax looks like this:

(function(){
// do something here
})():

Sometimes you'll see arguments passed in as well. It's basically used to wrap your code so none of your variables leak out into the global namespace.

1 Answers1