操作ClassName的工具函数(JavaScript权威指南）

/**
* CSSClass.js
*/
var CSSClass = {}; //Create our namespace object
//Return tru if element e is a member of the class c;false otherwise
CSSClass.is = fucntion(e, c)
{
if(typeof e == "string")
e = document.getElementById(e);
//Before doing a regexp search,optimize for couple of common cases.
var classes = e.className;
if(!classes){return false;}
if(classes == c){return true;}

// Otherwise, user a regular expression to search for c as a word by itself
// \b in a regular expression requires a match at a word boundary,
return e.className.search("\\b" + c + "\\b") != -1;
};
// Add class c to the className of element e if it is not already there.
CSSClass.add = function(e, c)
{
if(typeof e == "string")
{
e = document.getElementById(e);
if(CSSClass.is(e, c))//If already amember, do nothing
{
return;
}

//Whitespace a separator, if needed
if(e.classeName)
{
c= ""+c
}
e.className = += c; //Append the new class to the end
}
};
//Remove all occurrences(if any) of class c from the className of element e
CSSClass.remove = function(e, c)
{
if(typeof e == "string")
{
e = document.getElementById(e);
}

//Search the className for all ovvurrences of c and replace with "".
// \s* matches any number of whitespace characters.
// "g" makes the regular expression match any number of occurrences.
e.className = e.className.replace(new RegExp("\\b" + c + "\\b\\s*", "g"), "");
};