JSFiddle - React, Tailwind, and code Playground

HTML

<input id="input" type="text">
<ul>
    <li id="plus">+1</li>
    <li id="minus">-1</li>
</ul>

JavaScript

$('#plus').click(function () {
    var currentVal = parseInt($('#input').val());
    $('#input').val( currentVal+1 );
});

$('#minus').click(function () {
    var currentVal = parseInt($('#input').val());
    $('#input').val( currentVal-1 );
});