我正在尝试递归遍历 HTML 文档的 DOM 并打印节点的名称，同时使用缩进来标识子节点。我修改了一个 w3schools 代码示例，结果如下:
<!DOCTYPE html>
<html>
<head>
<title> Test Example </title>
</head>
<body>
<p>Click the button to get the node names of the body element's child nodes.</p>
<button onclick="myFunction(document.documentElement)">Try it</button>
<p><strong>Note:</strong> Whitespace inside elements is considered as #text, and text is considered as nodes.</p>
<!-- My personal comment goes here.. -->
<div><strong>Note:</strong> Comments in the document are considered as #comments, and comments are also considered as nodes.</div>
<p id="demo"></p>
<script>
function myFunction(node) {
indent = "";
txt = node.nodeName + "<br>";
document.write(txt);
var c = node.childNodes;
var i;
for (i = 0; i < c.length; i++) {
myFunction(c[i], indent);
}
}
function myFunction(node, indent) {
var indent = indent + " ";
txt = indent + node.nodeName + "<br>";
document.write(txt);
var c = node.childNodes;
var i;
for (i = 0; i < c.length; i++) {
txt = c[i].nodeName + "<br>";
myFunction(c[i], indent);
}
}
</script>
</body>
</html>
我得到的结果是:
undefined HTML
undefined HEAD
undefined #text
undefined TITLE
undefined #text
undefined #text
undefined #text
undefined BODY
undefined #text
undefined P
undefined #text
undefined #text
undefined BUTTON
undefined #text
undefined #text
undefined P
undefined STRONG
undefined #text
undefined #text
undefined #text
undefined #comment
undefined #text
undefined DIV
undefined STRONG
undefined #text
undefined #text
undefined #text
undefined P
undefined #text
undefined SCRIPT
undefined #text
undefined #text
所以我有几个问题
1) 为什么不打印带有节点名称的缩进值，而是打印 undefined？
2) 如果我只询问节点名称，为什么还要打印#text 和#comments 行？
我对 HTML 和 javascript 很陌生，所以任何见解都会有所帮助
编辑
我解决了第二个问题，但我的第一个问题仍然存在。我的脚本现在看起来像
<script>
function myFunction(node) {
var indent = "";
txt = node.nodeName + "<br>";
document.write(txt);
var c = node.children;
var i;
for (i = 0; i < c.length; i++) {
myFunction(c[i], indent);
}
}
function myFunction(node, indent) {
indent = indent + " ";
txt = indent + node.nodeName + "<br>";
txt = txt.replace(/ /g, ' ');
document.write(txt);
var c = node.children;
var i;
for (i = 0; i < c.length; i++) {
txt = c[i].nodeName + "<br>";
myFunction(c[i], indent);
}
}
and my output looks like
undefined HTML
undefined HEAD
undefined TITLE
undefined BODY
undefined P
undefined BUTTON
undefined P
undefined STRONG
undefined DIV
undefined STRONG
undefined P
undefined SCRIPT
我显然还遗漏了什么，但我不明白是什么
编辑2
感谢下面的帮助，我弄清楚了我在第二个 myfunction(现在称为 myfunction1)循环中调用错误函数的问题
<!DOCTYPE html>
<html>
<head>
<title> Test Example </title>
</head>
<body>
<p>Click the button to get the node names of the body element's child nodes.</p>
<button onclick="myFunction(document.documentElement)">Try it</button>
<p><strong>Note:</strong> Whitespace inside elements is considered as #text, and text is considered as nodes.</p>
<!-- My personal comment goes here.. -->
<div><strong>Note:</strong> Comments in the document are considered as #comments, and comments are also considered as nodes.</div>
<p id="demo"></p>
<script>
function myFunction(node) {
var indent = "";
var txt = node.nodeName + "<br>";
document.write(txt);
var c = node.children;
var i;
for (i = 0; i < c.length; i++) {
myFunction1(c[i], indent);
}
}
function myFunction1(node, indent) {
indent = indent + " ";
txt = indent + node.nodeName + "<br>";
txt = txt.replace(/ /g, ' ');
document.write(txt);
var c = node.children;
var i;
for (i = 0; i < c.length; i++) {
txt = c[i].nodeName + "<br>";
myFunction1(c[i], indent);
}
}
</script>
</body>
</html>
现在输出
HTML
HEAD
TITLE
BODY
P
BUTTON
P
STRONG
DIV
STRONG
P
SCRIPT
最佳答案
1) why is it not printing the indent value with the node name and instead printing
undefined?
您有 2 个同名函数，请确保您运行的是正确的函数并提供正确的参数。从更新的输出中，您可以使用这样的代码在第一次调用时将 indent 初始化为空字符串。
function myFunction(node, indent) {
indent = (indent || "") + " ";
2) why is it printing the #text and #comments lines as well if I'm only asking for the nodes name?
因为这些也是节点(并且它们有名称)，并且您没有在代码中过滤掉它们。考虑仅通过元素递归，而不是所有 DOM 节点，如果您想排除它们，则使用 .children 而不是 .childNodes。
关于javascript - 递归遍历 HTML DOM 并打印属性，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36098066/