<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <title>j</title></head><body> <div class="box"> <div class="cute">11111</div> <div class="hh">aaaa</div> <div class="hh">bbbb</div> <div id="test">ccccc</div> <p>标签名实验</p> </div></body><script>
function $(param, obj) {
obj = obj || document; //根据id名查找元素 if (param[0] === "#") return document.getElementById(param.slice(1)); // 根据指定类名查找元素 if (param.indexOf(".") === 0) return getByClass(param.substring(1), obj); //根据标签名查找 return obj.getElementsByTagName(param);}//类名查找元素实现方法function getByClass(className, obj) { obj = obj || document; if (obj.getElementsByClassName) return obj.getElementsByClassName(className); var result = []; var tags = obj.getElementsByTagName("*"); for (var i = 0, len = tags.length; i < len; i++) { var classNames = tags[i].className.split(" "); // 获取当前遍历元素的类名 for (var j = 0, l = classNames.length; j < l; j++) { if (className === classNames[j]) { // 找到所需要进行查找的一个元素 result.push(tags[i]); break; } } } return result;}$("#test").style.background = "red";
$(".hh")[0].style.background = "blue"; $("p")[0].style.background = "green";</script>
</html>