通常先使用getElementsByTagName("*")取出文檔中所有元素，然后進(jìn)行遍歷，使用正則表達(dá)式找出匹配的元素放入一個(gè)數(shù)組返回。由于IE5不支持document.getElementsByTagName("*")，要使用分支document.all以防錯(cuò)誤

下面的方法完美支持了document寫法

復(fù)制代碼代碼如下:

if(!document.getElementsByClassName){ 
document.getElementsByClassName = function(className, element){ 
var children = (element || document).getElementsByTagName('*'); 
var elements = new Array(); 
for (var i=0; i<children.length; i++){ 
var child = children[i]; 
var classNames = child.className.split(' '); 
for (var j=0; j<classNames.length; j++){ 
if (classNames[j] == className){ 
elements.push(child); 
break; 
} 
} 
} 
return elements; 
}; 
}

最終的方案為：

復(fù)制代碼代碼如下:

var getElementsByClassName = function (searchClass, node,tag) { 
if(document.getElementsByClassName){ 
var nodes = (node || document).getElementsByClassName(searchClass),result = []; 
for(var i=0 ;node = nodes[i++];){ 
if(tag !== "*" && node.tagName === tag.toUpperCase()){ 
result.push(node) 
}else{ 
result.push(node) 
} 
} 
return result 
}else{ 
node = node || document; 
tag = tag || "*"; 
var classes = searchClass.split(" "), 
elements = (tag === "*" && node.all)? node.all : node.getElementsByTagName(tag), 
patterns = [], 
current, 
match; 
var i = classes.length; 
while(--i >= 0){ 
patterns.push(new RegExp("(^|\s)" + classes[i] + "(\s|$)")); 
} 
var j = elements.length; 
while(--j >= 0){ 
current = elements[j]; 
match = false; 
for(var k=0, kl=patterns.length; k<kl; k++){ 
match = patterns[k].test(current.className); 
if (!match) break; 
} 
if (match) result.push(current); 
} 
return result; 
} 
}