JSFiddle - React, Tailwind, and code Playground

by enagu

HTML

<input type="text" id="numbers">

JavaScript

let creditNumber = document.getElementById("numbers")
var espacios = 0;

creditNumber.addEventListener("keydown", function(event) {
    if((event.target.value.length - espacios) % 4 === 0) {
        event.target.value += " ";
        espacios++;
     }
})