javascript - 为什么即使有父项，我的所有父函数都返回null？ - Thinbug

为什么即使有父项，我的所有父函数都返回null？

时间：2016-04-05 08:03:01

标签： javascript html

注意：这是用于家庭作业，请仅以尊重学术诚信的方式回答。

每当我调用父节点时，它都会返回null，即使它有父节点，并且我知道如果没有父节点，它应该是这样做的。该程序应该显示DOM从父级到子级的层次结构。

的JavaScript

            var styleChange = "";
            function start() {
                window.addEventListener("mousedown", changeStyleTo, false);
            }

            window.addEventListener("load", start, false);

            function changeStyleTo(e) {
                e.target.setAttribute("style", "background-color: yellow; color: red");
                window.addEventListener("mouseup", changeStyleBack, false);
            }

            function changeStyleBack(e) {
                var current = e.target.cloneNode();
                window.alert(current.nodeName);

                var elementString = current.nodeName;

                for (var i = 0; i < document.body.childElementCount; i++) {
                    if (current != document.body) {
                        elementString += current.tagName;
                        current = current.parentNode;
                    }
                }
                window.alert("elementString");

                e.target.setAttribute("style", "background-color: white; color: black");
            }

HTML

    <body id="Body">
        <h1 id="H1">The 23<sup>rd</sup> Psalm</h1>
        <h2 id="H2">A Psalm of David.</h2>
        <ol id="Ol"> 
            <li id="Li1">
                The LORD is my shepherd; I shall not want.
            </li>
            <li id="li2">
                He maketh me to lie down in green pastures: he leadeth me beside the still waters.
            </li>
            <li id="li3">
                He restoreth my soul: he leadeth me in the paths of righteousness for his name's sake.
            </li>
            <li id="li4">
                Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me.
            </li>
            <li id="li5">
                Thou preparest a table before me in the presence of mine enemies: thou anointest my head with oil; my cup runneth over.
            </li>
            <li id="li6">
                Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the LORD for ever.
            </li>
        </ol>
        <hr id="Hr"/>
        <p id="p1">
            <del id="Del">
                &copy; 1611, THE MOST HIGH AND MIGHTY PRINCE JAMES, BY THE GRACE OF GOD KING OF GREAT BRITAIN, FRANCE, AND IRELAND, DEFENDER OF THE FAITH, etc.  <strong>All rights reserved.</strong>
            </del>
        </p>
        <p id="p2">
            <ins id="Ins">
                This text is in the <strong>Public Domain</strong>.
            </ins>
        </p>
        <p id="p3">
            Return to
            <a id="A" href="http://www.masters.edu" title="The Master's College Home Page">
                The Master's College
                <img src="masters.png" width="125" height="180" alt="The Master's College logo"/>
            </a>
        </p>
    </body>
</html>

1 个答案:

答案 0 :(得分：1)

而不是

var current = e.target.cloneNode();

写下这个：

var current = e.target;

此外，您的循环未进行优化，请移除循环并将if条件修改为while循环。