JSFiddle - React, Tailwind, and code Playground

HTML

<form name="fish">
    <input type="text" name="big" value="Big Fish">
    <input type="text" name="little" value="Little Fish">
    <input type="text" name="tiny" value="Tiny Fish" readonly>
</form>

CSS

input[readonly] {
    color: #999;
}

JavaScript

document.forms['fish']['big'].readOnly = true;