Why do you need to invoke an anonymous function on the same line?

Question

I was reading some posts about closures and saw this everywhere, but there is no clear explanation how it works - everytime I was just told to use it...:

//          


        

Answer 1

My understanding of the asker's question is such that:

How does this magic work:

(function(){}) ('input')   // Used in his example

I may be wrong. However, the usual practice that people are familiar with is:

(function(){}('input') )

The reason is such that JavaScript parentheses AKA (), can't contain statements and when the parser encounters the function keyword, it knows to parse it as a function expression and not a function declaration.

Source: blog post Immediately-Invoked Function Expression (IIFE)