Does IIFE always return undefined?

Question

In the code snipped below, why the content of variable foo is undefined? I was expecting our IIFE statement return something!

var foo = (function (){
    var a=8;
    console.log("hi");
})();

Answer 1

The function inside of your expression that you are invoking is not returning any values, so that is why foo is undefined. If it returned a value, then foo would contain that value.

var foo = (function(){
    var a = 8;
    console.log("hello");
    return "world";
})()
console.log(foo);//world