JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="email" />
<button type="button" id="submit">Test</button>

JavaScript

var $ = function (id) {
    return document.getElementById(id);
};



var validateEmail = function () {
    var email = $("email").value;
    var symbol = email.search("@");
    var domain = email.substring(email.indexOf('@')).substr(1);
    var validDomain = domain.search(/\./);

    if (symbol == -1) {
        alert(email + " is not a valid email address.");
    } else if (validDomain == -1) {
        alert(email + " is not a valid domain name.");
    } else {
        alert(email + " is a valid email address.");
    }
};

window.onload = function () {
    $("submit").onclick = validateEmail;
};