获取父级

的子级

的值

<div id="parent">
    <div id="child">
        some-value
    </div>
</div>

我如何获得“某些价值”？ 我试过

var parent = document.getElementById("parent");
var child = parent.childNodes[0];
var childval = child.value;
document.getElementById("output").innerHTML=childval;

它输出“未定义”。

The value property only exists for form elements. If you want to get the content of any other elements, you can either use innerHTML [MDN] to get the content as HTML string, or textContent [MDN] resp. innerText [MSDN] to only get the text content without HTML tags.

childNodes [MDN] returns all child nodes, not only element nodes. That means, it also contains text nodes for example. The line break you have after <div id="parent"> is a text node as well. Hence, parent.childNodes[0] returns the text node which consists only of a line break.

If you want to get the first element node, you can either use children [MDN] (see browser compatibility), or iterate over the child nodes, testing what kind of node each of them is. 1 indicates an element node, 3 a text node:

var child = parent.firstChild;

while(child && child.nodeType !== 1) {
    child = child.nextSibling;
}

There are also other ways to retrieve elements, e.g. with getElementsByTagName [MDN].

Or in your case, you can just use getElementById [MDN] to get a reference to both of the elements.