Money Formatter

HTML

<span class="money">1234</span>
<span class="money">123456789</span>
<span class="money">123424.97</span>
<span class="money">123.23</span>
<span class="money">12.34</span>
<button onclick="format()">
Format those guys
</button>

CSS

.money{
  display: block;
}

JavaScript

function format(){
	var dollars = document.getElementsByClassName('money');
  for(var i = 0; i < dollars.length; i++){
  	dollars[i].innerHTML = dollars[i].innerHTML.replace(/(\d{1,3})(?=\d{3})/g, '$1,');
  }
}