lib/Ext/dom/Element.style.js
function(className, force){
        if (typeof force !== 'boolean') {
            force = !this.hasCls(className);
        }

   		return (force) ? this.addCls(className) : this.removeCls(className);
   	}
function(className, force){
        if (typeof force !== 'boolean') {
            force = !this.hasCls(className);
        }

   		return (force) ? this.addCls(className) : this.removeCls(className);
   	}
Toggles the specified CSS class on this element (removes it if it already exists, otherwise adds it).
@param {String} className The CSS class to toggle.
@return {Ext.dom.Element} this