lovecoding
/
W250913


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 400px;
            height: 400px;
            border:3px solid black;
        }
        .box1{
            width: 200px;
            height: 200px;
            background-color: red;
        }
        .box2{
            width: 200px;
            height: 200px;
            background-color: blue;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="box2"></div>
    </div>
    <button class="btn">add</button>
    <script>
        var oBtn = document.getElementsByClassName("btn")[0];
        var oBox = document.getElementsByClassName("box")[0];
        var oBox2 = document.getElementsByClassName("box2")[0];
        oBtn.onclick = function(){
            // oBox.innerHTML = "<div class=box1></div>"
            // createElement 创建新的元素
            var newElement = document.createElement("div");
            newElement.innerText = "hello";
            newElement.classList.add("box1");
            // console.log(newElement);
            // append 向当前元素最后添加一个新的元素
            // oBox.append(newElement);
            // insertBefore 也可以向元素内添加节点 后边两个参数第一个 你要插入元素 第二个插入到谁的前面
            oBox.insertBefore(newElement,oBox2);
        }
    </script>
</body>
</html>