Use of IIFE in ES6

In ES5 it is considered good practice to use IIFE to force a local scope in our code. EX: 

(function(){
  // some code
})();

In ES6 is this still necessary? Once the keyword let has been introduced for variable declaration?

Thank you.

Author: Vinicius Brasil, 2019-03-27
Source

1 answers

When declaring variables with var in JS, you had to create a new lexical scope so as not to mess up the window (in most cases).

var abc = 1;

console.log(abc);
// => 1

console.log(window.abc);
// => 1

The simplest way was to create a function and call it right after, since JavaScript functions create a new lexical scope. As you mentioned, they are the IIFE (Immediately Invoked Function Expressions): 

(function(){
  var abc = 1;
})();

console.log(abc);
// => Uncaught ReferenceError: abc is not defined

But in ES6, with the introduction of let and const, which are block-scoped declarators, this is really no longer I need it. For other uses, such as creating a namespace, or scoping variables, you still need to create a new lexical scope. But you don't need to use IIFE, in ES6+ just create a block ({ ... }).

let x = 1;

{
  let x = 2;
}

console.log(x);
// => 1

As you may already know, all this is because:

  • var is scoped by function
  • let and const are scoped by block
 1
Author: Vinicius Brasil, 2019-03-28 03:58:42