JSFiddle - React, Tailwind, and code Playground

HTML

<a href = "https://i.ytimg.com/vi/Q5TySBfGHMI/hqdefault.jpg?custom=true&w=196&h=110&stc=true&jpg444=true&jpgq=90&sp=68&sigh=2gQERl4mfDDvpbEgtAlORMFuX6A" download = "filename.jpg" id = "download">Click here to download image</a>
<canvas></canvas>

JavaScript

setTimeout(function(){
  downloadCanvas();
}, 4E3);

function downloadImage(){
  document.getElementById('download').click();
}

function downloadCanvas(){
  var a = document.getElementById('download');
  var b = a.href;
  a.href = document.getElementsByTagName('canvas')[0].toDataURL();
  downloadImage();
  a.href = b;
}