JSFiddle - React, Tailwind, and code Playground

by Rahul Desai

HTML

<input type="text" id="input" />
<input type="submit" value="Check" id="submit" />

JavaScript

var buttonElement = document.getElementById("submit");

buttonElement.addEventListener('click', check, false);

function check(){
    var number = document.getElementById('input').value;
    if(number.charAt(0) === 0)
        alert('Leading zero in the input.')
    else
        alert('No leading zero in the input.')
}