daily_notes/DOM_function.html at master · shiaoyi/daily_notes · GitHub

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<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Page Title</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="screen" href="main.css">
    <script src="main.js"></script>
    <style type="text/css">
        html,body{
            margin: 0px;
        }

        .yellow{
            background-color: yellow;
        }
    </style>
    <script type="text/javascript">
        document.addEventListener('DOMContentLoaded',function(){
            //getElementById用來指到id
            var idtest = document.getElementById('idtest');
            //getElementsByClassName可用來指很多class
            var classtest = document.getElementsByClassName('classtest');
            //querySelector指class或id都行，這裡只指到test下第一個p，>沒有也沒關係
            var test = document.querySelector(".test > p");
            test.style.color = "green";
            //如果要選到test下面全部的p，就要用querySelectorAll，再用test[0]陣列的方式去指定
            //test[0]是Hello，test[1]是Welcome

            //createElement用來製造元素節點
            var span = document.createElement("span");
            //appendChild是在畫面新增一個節點，所以後面要接一個節點
            test.appendChild(span);
            //所以appendChild和createElement能結合成一個式子
            test.appendChild(document.createElement("span"));

            //classList用來添加元素的class，所以根據style裡的yellow class，span的背景會變黃的
            span.classList.add("yellow");
            span.innerHTML = " Sunny!";

            //用toggle做按鈕互動，toggle像開關鍵，開sunny背景會變亮黃，關會無背景色
            document.querySelector('#btn').addEventListener('click', () =>{
                document.querySelector('.test span').classList.toggle('yellow');
            })
        })

    </script>
</head>
<body>
    <div id="idtest"></div>
    <div class="test">
        <p class="classtest">Hello</p>
        <p class="classtest">Welcome</p>
    </div>
    <input type="button" id="btn" value="click me" />
</body>
<script type="text/javascript" >

</script>
</html>