console 命令行工具 X clear

console

window.onload = function(){

    //找到父元素
    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 = "lightskyblue";
        }
    }


    //找子元素和子节点

    var oUl = document.getElementById("list");
    var oChildElements = oUl.children;
    var ochildNodes = oUl.childNodes;
    console.log("line 19:" + oChildElements.length);
    console.log("line 20:" + ochildNodes.length);

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

    oBtn.onclick = function(){
        //删除最后一个子节点
        //oUl.removeChild(oUl.lastChild);

        //删除元素节点
        //if(oUl.lastChild.nodeType == 3){
        //    oUl.removeChild(oUl.lastChild);
        //    oUl.removeChild(oUl.lastChild);
        //}
        //else{
        //    oUl.removeChild(oUl.lastChild);
        //}
        //oUl.removeChild(oUl.lastElementChild);
        //oUl.removeChild(oUl.firstElementChild);
        oUl.removeChild(oUl.firstChild);

        //删除兄弟元素节点
        var oCSS = oUl.children[1];
        //oUl.removeChild(oCSS.previousElementSibling);
        //oUl.removeChild(oCSS.nextElementSibling);

        //删除兄弟节点
        //oUl.removeChild(oCSS.previousSibling);
        //oUl.removeChild(oCSS.nextSibling);
    }
}

<!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;
}