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<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title><style>.one {width:300px;height:300px;background-color:red;}</style></head><body><div class="one">hhhhhhhhh</div><div class="one three">eeeeeeeeeeee</div><div class="one two">llllllllllllll</div><div class="one two three">pppppppppppp</div><h3 class="one">11111111111111</h3><h3>2222222222222</h3><p class="one">33333333333333</p></body></html><script>var ones = gclass("one");console.log(ones);for(var i = 0; i < ones.length; i++) {ones[i].style.backgroundColor = "green";}// 通过类名获取所有元素的方法function gclass(className, tagName) {// var alltags = document.all;var alltags = document.getElementsByTagName(tagName || "*");var arr = new Array();for(let i = 0; i < alltags.length; i++) {// one two// split把一个字符串分割成字符串数组:var one = className.split(" ");var two = alltags[i].className.split(" ");if(isHasArray(one, two)) {arr[arr.length] = alltags[i];}}//返回所有类元素集合return arr;}// 判断一个数组中的所有元素是否在另外的一个数组中存在function isHasArray(one, two) {if(two.length < one.length){return false;}var flag = 0;for(let i=0; i<one.length; i++) {for(let j=0; j<two.length; j++) {if(one[i]==two[j]){flag++;break;}}}return flag == one.length;}</script>
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