How to execute a function once in JavaScript

In this Article we will go through how to execute a function once only using single line of code in JavaScript. This is a one-line JavaScript code snippet that uses one of the most popular ES6 features => Arrow Function.

Let's define this short function:

const once = fn => ((ran = false) => () => ran ? fn : (ran = !ran, fn = fn()))();

let n = 0;
const incOnce = once(() => ++n);
incOnce();      // n = 1
incOnce();      // n = 1
incOnce();      // n = 1