Called as “Iffy” ( IIFE - immediately invoked function expression) is an anonymous function expression that is immediately invoked and has some important uses in Javascript.


(function() {
 // Do something​
 }
)()

It is an anonymous function expression that is immediately invoked, and it has some particularly important uses in JavaScript.

The pair of parenthesis surrounding the anonymous function turns the anonymous function into a function expression or variable expression. So instead of a simple anonymous function in the global scope, or wherever it was defined, we now have an unnamed function expression.

Similarly, we can even create a named, immediately invoked function expression:

(someNamedFunction = function(msg) {
	console.log(msg || "Nothing for today !!")
	}) (); // Output --> Nothing for today !!​
​
someNamedFunction("Javascript rocks !!"); // Output --> Javascript rocks !!
someNamedFunction(); // Output --> Nothing for today !!​

For more details, check the following URL’s -

  1. Link 1
  2. Link 2

Performance: jsPerf