JSFiddle - React, Tailwind, and code Playground

HTML

<form action="process.php" method="POST" enctype="multipart/form-data" id="add_prod_form">
Item Name: <input type="text" name="add_prod_name" id="add_prod_name"/><br /><br />
Image 1: <input type="file" name="add_prod_image[]" id="add_prod_image"/><br /><br />
Image 2: <input type="file" name="add_prod_image[]" /><br /><br />
Image 3: <input type="file" name="add_prod_image[]" /><br /><br />
Image 4: <input type="file" name="add_prod_image[]" /><br /><br />
Image 5: <input type="file" name="add_prod_image[]" /><br /><br />
Short description:<br />
<textarea rows="7" cols="50" name="add_prod_description_short" id="add_prod_description_short"/></textarea><br />
Long description:<br />
<textarea rows="7" cols="50" name="add_prod_description_long" id="add_prod_description_long"/></textarea><br /><br />
Price: <input type="text" name="add_prod_price" id="add_prod_price"/><br /><br />
<input type="hidden" name="action" value="add_product" />
<input type="submit" name="submit" id="add_prod_submit" disabled="disabled">

JavaScript

$('#add_prod_name, #add_prod_image, #add_prod_description_short, #add_prod_description_long, #add_prod_price').keyup(function() {
    if(allFilled()){
         $('#add_prod_submit').removeAttr('disabled');
    }
});

function allFilled() {
    var filled = true;
    $('#add_prod_form input, textarea').not('#add_prod_submit').each(function() {
        if($(this).val() == '') filled = false;
    });
    return filled;
}