Introduction
IIFEs (Immediately-Invoked Function Expressions), pronounced “Iffys”, are functions that are immediately executed without you having to explicitly call them.
In the example below, we will have the console.log log to the console without having to do anything. This is because the function is automatically being called.
(function () {
console.log('This function is called as soon as the function is defined');
})();
Notes regarding IIFE
There are major important parts of an IIFE to take note of:
-
There is an anonymous function that prevents variables inside the IIFE from polluting the global scope.
-
After the function is the invoked function expression
()which causes the function to be called.
Use cases
An IIFE on its own is useful, however it forms the basis of the module pattern which we will cover shortly.