JSFiddle - React, Tailwind, and code Playground

HTML

<div class="span24 overview overview-small">

JavaScript

var spans = $('div[class*=span]');
spans.each(function(index,element){
     var spanClass = element.className;
     var tar = spanClass.indexOf("span");
     var number = "";
     for( var i = (tar + 4); i < spanClass.length; i++ ){
      if( spanClass[i] == " " ) break;
      number += spanClass[i].toString();
     }
     number = parseInt(number);
     alert(number);
    });