JSFiddle - React, Tailwind, and code Playground

HTML

<div>canvas:</div>
<canvas width="100" height="100"></canvas>

CSS

::selection {
  background: transparent;
  // color: currentColor;
} 
 
::-moz-selection {
  background: transparent;
  // color: currentColor;
}
  
* {
  user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  -o-user-select: none;
  -webkit-user-select: none;
}

JavaScript

var elements = document.getElementsByTagName('*');

for (var i = 0; i < elements.length; i++) {
  elements[i].setAttribute('unselectable', 'on');
}