JSFiddle - React, Tailwind, and code Playground

by Sean Cannon

HTML

<input id="input1"/>
<input id="input2"/>

JavaScript

(function() {
    var input1   = document.getElementById('input1'),
        input2   = document.getElementById('input2'),
        callback = function () {
            input2.value = this.value;
        };

    if (input1.addEventListener) {
        input1.addEventListener('keyup', callback);
    } else {
        input1.attachEvent('onkeyup', callback);
    }
}());