JSFiddle - React, Tailwind, and code Playground

HTML

<label for="edQuantity">Quantity:</label>
<input id="edQuantity" type="number" 
    onchange="edQuantityChange(this, event)"
    onkeyup="edQuantityChange(this, event)">
        
<p>edQuantity.value = <span id="lblValue"></span>
   
<p><p><p>
<input type="submit">

CSS

:invalid {
    background: #FCC;
}
:valid {
    background: #CFF;
}

JavaScript

function edQuantityChange(sender, event)
{
    var value = sender.value;
    
    var lblValue = document.getElementById("lblValue");
    lblValue.innerText = value;
}