JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="fDisableSelect('webkit')">webkit</button>
<button onclick="fDisableSelect('Moz')">moz</button>
<button onclick="fDisableSelect('ms')">ms</button>

<p>Select this</p>

<p class='predefined'>
  Predefined
</p>

CSS

.predefined{
  -webkit-user-select:none;
  -moz-user-select:none;
  -ms-user-select:none;
}

p{
  font-size:32px
}

JavaScript

function fDisableSelect(pPre){
    document.body.style[pPre + 'UserSelect'] = 'none';
}