JSFiddle - React, Tailwind, and code Playground

HTML

<span class='pups'>100</span>
<span class='pups'>2000</span>
<span class='pups'>30000</span>
<span class='pups'>400000</span>
<span class='pups'>5000000</span>
<span class='pups'>60000000</span>
<span class='pups'>700000000</span>

CSS

span {
  display: block;
}

JavaScript

$('.pups').each(function() {
	var ns = (parseInt(this.textContent) * 10).toString();
	var l = ns.length;
	var first = (l % 3 === 0) ? 3 : l % 3;

	var s = ns.substr(0, first);
	for(var i=first; i<l; i+=3) {
    s += ' ' + ns.substr(i, 3);
	}
  
  this.textContent = s;
})