addClass, removeClass, toggleClass（从jquery中抠出来）

<div id="d3" class="cur"></div>

var mylibs = (function(){
    var rtrim = /^[suFEFFxA0]+|[suFEFFxA0]+$/g,
        core_trim = String.prototype.trim,
        core_rspace = /s+/,
        rclass = /[	
]/g;
        
    var trim = function(text){
        if(core_trim && !core_trim.call("uFEFFxA0")){
            return text == null ?
                "" :
                core_trim.call(text);
        }else{
            return text == null ?
                "" :
                (text + "").replace(rtrim, "");
        }
    };
            
    return {
        addClass:function(elem,value){
            var classNames,setClass;
            
            if (!value || typeof value !== "string") return;
            if (elem.nodeType !== 1) return;
            
            classNames = value.split(core_rspace);
            
            if (!elem.className && classNames.length === 1){
                elem.className = value;
            }else{
                setClass = " " + elem.className + " ";
            
                for (var i = 0; i < classNames.length; i++){
                    if (setClass.indexOf(" " + classNames[ i ] + " ") < 0)
                        setClass += classNames[ i ] + " ";
                }
                elem.className = trim(setClass);
            }    
        },
        removeClass:function(elem,value){
        
            var removes,className;
        
            if ((!value || typeof value !== "string") && value !== undefined) return;
            if (elem.nodeType !== 1 || !elem.className) return;
            
            removes = (value || "").split(core_rspace);
            className = (" " + elem.className + " ").replace(rclass," ");
            
            // loop over each item in the removal list
            for (var i=0;i<removes.length;i++){
                // Remove until there is nothing to remove,
                while (className.indexOf(" " + removes[i] + " ") >= 0)
                    className = className.replace(" " + removes[i] + " "," ");
            }
            elem.className = value ? trim(className) : "";
        },
        toggleClass:function(elem,value,stateVal){
            var type = typeof value,
                isBool = typeof stateVal === "boolean";
        
            if (type !== "string") return;
            
            // toggle individual class names
            var className,
                i = 0,
                state = stateVal,
                classNames = value.split(core_rspace);
    
            while ((className = classNames[ i++ ])){
                // check each className given, space separated list
                state = isBool ? state : !this.hasClass(elem,className);
                (state ? this['addClass'] : this['removeClass'])(elem,className);
            }
        },
        hasClass:function(elem,selector){
            var className = " " + selector + " ";
            if (elem.nodeType === 1 && (" " + elem.className + " ").replace(rclass," ").indexOf(className) >= 0)
                return true;
            return false;
        }
    };
})();

var dom = document.getElementById('d3');
mylibs.addClass(dom,'red');
mylibs.removeClass(dom,'cur');
mylibs.toggleClass(dom,'red cur');