console 命令行工具 X clear

console

window.onload = function () 
{
    //找到所有的td元素
    var oTds=document.getElementsByTagName("td");
    
    //给每一个td元素添加点击事件
    for(var i=0;i<oTds.length;++i){
        oTds[i].onclick=function(){
            //获取当前td的父元素tr
            var oParent=this.parentNode;
            //为父元素添加样式
            oParent.style.color="white";
            oParent.style.backgroundColor="lightskyblue";
        }
    }

    var oUl=document.getElementById("list");
    var oChildNodes=oUl.childNodes;
    var oChildElements=oUl.children;

    console.log("There are"+oChildNodes.length+"child nodes in list.");
    console.log("There are"+oChildElements.length+"child element nodes in list.");

    var oBtn=document.getElementById("btn");

    oBtn.onclick=function(){
        //删除最后的子节点
        //oUl.removeChild(oUl.lastChild);

        //删除最后的元素节点
        //if(oUl.lastChild.nodeType==3){
        //    oUl.removeChild(oUl.lastChild);
        //    oUl.removeChild(oUl.lastChild);
        //}else{
        //    oUl.removeChild(oUl.lastChild);
        //}

        //oUl.removeChild(oUl.lastElementChild);

        //删除兄弟元素节点
        //var preLastElement=oUl.lastElementChild.previousElementSibling;
        //oUl.removeChild(preLastElement);

        //删除兄弟节点
        var preLastNode=oUl.lastElementChild.previousSibling;
        oUl.removeChild(preLastNode);
    }
}

<!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;
}