JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<!DOCTYPE html>
<html>
    <head>
        <style>
        </style>
        <script type="text/javascript" src="js/jquery-1.5.min.js"></script>
        <script type="application/javascript">
            var x = 150;
            var y = 150;
            var dx = 2;
            var dy = 2;
            var width;
            var height;
            var canvas;
            var ctx;
            var rightDown = false;
            var leftDown = false;
            var upDown = false;
            var downDown = false;
            var intervalId = 0;

            function onKeyDown(evt) {
                if (evt.keyCode == 40) { downDown = true;}
                if (evt.keyCode == 39) { rightDown = true;}
                if (evt.keyCode == 38) { upDown = true;}
                if (evt.keyCode == 37) { leftDown = true;}
            }
            
            function onKeyUp(evt) {
                if (evt.keyCode == 40) { downDown = false;}
                if (evt.keyCode == 39) { rightDown = false;}
                if (evt.keyCode == 38) { upDown = false;}
                if (evt.KeyCode == 37) { leftDown = false;}
            }

            $(document).keydown(onKeyDown);
            $(document).keyup(onKeyUp);
            
            function init() {
                canvas = document.getElementById("canvas");
                ctx = canvas.getContext("2d");
                width = $("#canvas").width();
                height = $("canvas").height();
                intervalId = setInterval(draw, 10);
                return intervalId;
            }
            function circle(x,y,r) {
                ctx.beginPath();
                ctx.arc(x, y, r, 0, Math.PI*2, true);
                ctx.closePath();
                ctx.fill();
            }

            function clear() {
                ctx.clearRect(0,0,width,height);
            }
            function draw() {
               ...

JavaScript

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