function addClass(obj,sClass){

var aClass=obj.className.split(' ');

if(!obj.className){

obj.className=sClass;

return;

}

for(var i=0;i<aClass.length;i++){

if(aClass[i] === sClass)return;

}

obj.className+=' '+sClass;

}

function removeClass(obj,sClass){

var aClass=obj.className.split(' ');

if(!obj.className)return;

for(var i=0;i<aClass.length;i++){

if(aClass[i] === sClass){

aClass.splice(i,1);

obj.className=aClass.join('');

break;

}

}

}

不用自己寫(xiě)的，用classList或是jq的addclass就行了

function?addClass(element,newclass){
????if(element.className){
????????oldClass=element.className;
????????element.className=oldClass+"?"+newclass;
????}else{
????????element.className=newclass;
????}
}