SOURCE

console 命令行工具 X clear 

                    

                        
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console

            
window.onload=function(){
    var OTds=document.getElementsByTagName("td")

    for(var i=0;i<OTds.length; i++){
        OTds[i].onclick=function(){
            var oParent=this.parentNode;
            oParent.style.color="white"
            oParent.style.backgroundColor="red"
        }
    }

    var oUI=document.getElementById("list")
    var oChildNodes=oUI.childNodes;
    var oChildelement=oUI.children;
    console.log(oChildNodes.length)
     console.log(oChildelement.length)

    var oBtn=document.getElementById("btn")
    oBtn.onclick=function(){
        // oUI.removeChild(oUI.lastElementChild)
        // var prelast=oUI.lastElementChild.previousSibling;
        var prelast=oUI.lastElementChild.previousElementSibling;
        oUI.removeChild(prelast)

    }
}

            
<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <style type="text/css">
        
    </style>
    <script>
       
    </script>
</head>
<body>
    <table>
        <caption>考试成绩表</caption>
        <tr>
            <td>小明</td>
            <td>80</td>
            <td>80</td>
            <td>80</td>
        </tr>
        <tr>
            <td>小红</td>
            <td>90</td>
            <td>90</td>
            <td>90</td>
        </tr>
        <tr>
            <td>小杰</td>
            <td>100</td>
            <td>100</td>
            <td>100</td>
        </tr>
    </table>

    <ul id="list">
        <li>HTML</li>
        <li>CSS</li>
        <li>JavaScript</li>
        <li>jQuery</li>
        <li>Vue.js</li>
    </ul>
    <button id="btn">删除</button>
</body>
</html> 

            
table{
    border-collapse:collapse;
}
table,tr,td{
    border:1px solid gray;
}