JSFiddle - React, Tailwind, and code Playground

HTML

<form name="testform" onSubmit="return validate(this)">
<table width="650" border="0">

<tr>
 <td width="79" valign="top">
  <label for="Full_Name">Full Name<span class="required_star"> * </span></label>
 </td>
 <td width="289" valign="top">
  <input size="15" type="text" name="Full_Name" id="Full_Name" maxlength="50" value="" />
 </td>
</tr>
<tr>
 <td colspan="4" style="text-align:center">
  <input type="submit" value="Proceed"/>
 </td>
</tr></table>
</form>

JavaScript

function validate(el) {
if (el.Full_Name.value == "") {
     alert("Cannot leave area field blank!");
     return false;
 }
}