JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="nospace" />

JavaScript

window.onload = function () {
    var inputEl = document.getElementById("nospace");
    inputEl.addEventListener("keydown", function (e) {
        if (inputEl.value.length == 0) {
            if (e.keyCode == 32) {
                e.preventDefault();
            }
        }
    });
}