Remove specified class - vanilla JS

remove_class.js

// removeClass, takes two params: element and classname
function removeClass(el, cls) {
  var reg = new RegExp("(\\s|^)" + cls + "(\\s|$)");
  el.className = el.className.replace(reg, " ").replace(/(^\s*)|(\s*$)/g,"");
}

What do you think about this

function removeClass(el, cls) {
    'use strict';
    if ( hasClass(el, cls) ) {
        var newElementClass = ' ' + el.className + ' ';
        var newClassName = ' ' + cls + ' ';

        var re = new RegExp(''+newClassName+'', 'g');
        newClassName = newElementClass.replace(re, '');
        newClassName = newClassName.replace(' ', ''); 
        // or can use String method trim e.g newClassName.trim()

        el.className = newClassName;
    }
}