js判断样式className同时增加class或删除class

function MyClass () {}
MyClass.hasClassName = function(element, className)
{
if (!element) return;
var elementClassName = element.className;
if (elementClassName.length == 0) return false;
//用正则表达式判断多个class之间是否存在真正的class（前后空格的处理）
if (elementClassName == className || elementClassName.match(new RegExp("(^|\\s)" + className + "(\\s|$)")))
return true;
return false;
};
MyClass.addClassName = function(element, className)
{
if (!element) return;
var elementClassName = element.className;
if (elementClassName.length == 0)
{
element.className = elementClassName;
return;
}
if (elementClassName == className || elementClassName.match(new RegExp("(^|\\s)" + className + "(\\s|$)")))
return;
element.className = elementClassName + " " + className;
};
MyClass.removeClassName = function(element, className)
{
if (!element) return;
var elementClassName = element.className;
if (elementClassName.length == 0) return;
if(elementClassName == className)
{
element.className = "";
return;
}
if (elementClassName.match(new RegExp("(^|\\s)" + className + "(\\s|$)")))
element.className = elementClassName.replace((new RegExp("(^|\\s)" + className + "(\\s|$)"))," ");
};