JSFiddle - React, Tailwind, and code Playground

HTML

<form name="form" action="index.html" onsubmit="return construct();" method="post">
    <label>Your Name:<span class="req">*</span> 
    </label>
    <input type="text" name="name" />
    <br />
    <label>Company Name:<span class="req">*</span> 
    </label>
    <input type="text" name="companyName" />
    <br />
    <label>Phone Number:</label>
    <input type="text" name="phone" />
    <br />
    <label>Email Address:<span class="req">*</span>
    </label>
    <input type="text" name="email" />
    <br />
    <label>Best Time to be Contacted:</label>
    <input type="text" name="TimeForContact" />
    <br />
    <label>Availability for Presenting:</label>
    <input type="text" name="aval" />
    <br />
    <label>Message:</label>
    <textarea name="message" ROWS="3" COLS="30"></textarea>
    <label>First Time Presenting for AGC?:<span class="req">*</span>
    </label>
    <input type="radio" name="firstTime" value="Yes" id="yes" /><span class="small">Yes</span>

    <input type="radio" name="firstTime" value="No" id="no" /><span class="small">No</span>
    <br />
    <br />
    <input type="submit" name="submit" value="Sign-Up" />
</form>

JavaScript

function construct() {
    console.log("calling construct!");
    var name = document.forms["form"]["name"].value;
    var companyName = document.forms["form"]["companyName"].value;
    var email = document.forms["form"]["email"].value;
    var phone = document.forms["form"]["phone"].value;
    var TimeForC = document.forms["form"]["TimeForContact"].value;
    var availability = document.forms["form"]["aval"].value;

    if (!validateExistence(name)) return false;
    
    if (!validateExistence(companyName)) return false;
    
    if (radioCheck() == false) return false;
    if (phoneValidate(phone) == false) return false;
    if (checkValidForOthers(TimeForC) == false || checkValidForOthers(availability) == false) return false;
    if (emailCheck(email) == false) return false;
}

function validateExistence(name) {
    if (!name) {
        alert("You must enter a " + name + " to submit! Thank you.");
    return false;
    }
    if (name.length > 40) {
        alert(name + " is too long for our form, please abbreviate.");
    return false;
    }
    return true;
}

function phoneValidate(phone) {
    if (!phone || phone.length > 12 || isNaN(phone)) {
        alert("Please enter a valid phone number.");
    return false;
    }
    return true;
}

function checkValidForOthers(name) {
    if (name.length > 40) {
        alert(name + " is too long for our form, please abbreviate.");
    return false;
    }
    return true;
}

function messageCheck(message) {
    var currentLength = name.length;
    var over = 0;
    over = currentLength - 200;

    if (name.length > 200) {
        alert(name + " is too long for our form, please abbreviate. You are " + over + " characters over allowed amount");
    return false;
    }
    return true;
}

function radioCheck() {
    if (document.getElementById("yes").checked == false && document.getElementById("no").checked == false) {
        alert("click yes or no");
        return false;
    }
    return true;
}

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