JSFiddle - React, Tailwind, and code Playground

HTML

<canvas id="drawhere_cicles3" width="300" height="300"></canvas>
<script src='http://greenethumb.com/canvas/circles/circles3.js'></script>
<input type="submit" id="savepng" value="Save" />

JavaScript

var canvas = document.getElementById("drawhere_cicles3");
 

$("savepng").onclick = function() {
var cs = new CanvasSaver('http://greenethumb.com/canvas/lib/saveme.php');
cs.savePNG(canvas, 'image');

function CanvasSaver(url) {
  this.url = url;
  this.savePNG = function(cnvs, fname) {
  if(!cnvs || !url) return;
    fname = fname || 'picture';

    var data = cnvs.toDataURL("image/jpeg");
    data = data.substr(data.indexOf(',') + 1).toString();
    var dataInput = document.createElement("input") ;
    dataInput.setAttribute("name", 'imgdata') ;
    dataInput.setAttribute("value", data);

    var nameInput = document.createElement("input") ;
    nameInput.setAttribute("name", 'name') ;
    nameInput.setAttribute("value", fname + '.jpeg');

    var myForm = document.createElement("form");
    myForm.method = 'post';
    myForm.action = url;
    myForm.appendChild(dataInput);
    myForm.appendChild(nameInput);

    document.body.appendChild(myForm) ;
    myForm.submit() ;
    document.body.removeChild(myForm) ;
  };
}
}