JSFiddle - React, Tailwind, and code Playground

HTML

<div class="field">
        <label>remarks:</label>
        <textarea id="id_remarks" name="remarks"></textarea>
 </div>
<input type="submit" value="Save" onclick="verify()"/>

JavaScript

function verify(){
    if (!document.getElementById('id_remarks').value.trim()) {
        alert('Please enter the remarks');
    }
     else{
     alert(document.getElementById('id_remarks').value);
     }
 }