JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="setKeyDown()">Start KeyDown</button>
<button onclick="unsetKeyDown()">Stop KeyDown</button>

JavaScript

function setKeyDown () {
  //$(document).unbind('keydown');
  $(document).keydown( function(e) {
        switch (e.keyCode || e.which) {
        case 38:
            $('body').append('<p>up');
            break;
        case 40:
            $('body').append('<p>down');
            break;
    }
  });
}

function unsetKeyDown () {
   $(document).unbind('keydown');
}