JSFiddle - React, Tailwind, and code Playground

HTML

<div class="method">
     <h3>Method 1</h3>
    <form>
        <input value="Hello" style="width:30px;" />
        <input type="submit" />
    </form>
</div>
<div class="method">
     <h3>Method 2</h3>
    <form id="f2">
        <input value="Hello" style="width:30px;" />
        <input type="submit" />
    </form>
</div>

CSS

.method{
    float:left;
    width:100px;
    border:2px solid red;
    margin: 1px;
}

JavaScript

// method 1
document.getElementsByTagName("input")[1].onclick = function () {
    this.disabled = true;
};

// method 2
document.getElementById("f2").onsubmit = function() {   
    this.children[1].disabled = true;
    return false; // prevent form from actually posting (only for demo purposes)
}