getElementsByClassName不返回长度

Question

I want to get the length of the returned class names 我想得到返回的类名的length

There are a series of buttons that I want to add event listeners to and they all share the same class name. 有一系列按钮我想要添加事件监听器，它们都共享相同的类名。

removeButton = document.getElementsByClassName("removeButton");

When I do removeButton.length I always get 0 but if I do: 当我执行removeButton.length我总是得到0但如果我这样做：

console.log(removeButton) I can see the list of items there. console.log(removeButton)我可以看到那里的项目列表。

I need the length so I can iterate through a for-loop and assign the event listeners. 我需要长度，所以我可以迭代for-loop并分配事件监听器。

What seems to be the problem? 什么似乎是问题？

Solution 解
Check that the elements exist before trying to gather them with getElementsByClassName 在尝试使用getElementsByClassName收集元素之前，请检查元素是否存在

Answer 1

You have to be sure the elements exist if your JavaScript code depends on them. 如果JavaScript代码依赖于它们，则必须确保元素存在。

One way of achieving this by putting the <script> tag at the end of the body like this: 实现此目的的一种方法是将<script>标记放在正文的末尾，如下所示：

<html>
<head></head>
<body>
<script type="text/javascript">
    // code here
</script>
</body>

You can also put all your code in a function for the window.onload event or use a library that provides this functionality, such as jQuery . 您还可以将所有代码放在window.onload事件的函数中，或者使用提供此功能的库，例如jQuery 。

Answer 2

As OP stated, 正如OP所说，

Check that the elements exist before trying to gather them with getElementsByClassName. 在尝试使用getElementsByClassName收集元素之前，请检查元素是否存在。

getElementsByClassName不返回长度

问题描述

2 个解决方案

解决方案1
2 已采纳 2013-01-25 05:59:46

解决方案2
1

getElementsByClassName不返回长度

问题描述

2 个解决方案

解决方案1 2 已采纳 2013-01-25 05:59:46

解决方案2 1

解决方案1
2 已采纳 2013-01-25 05:59:46

解决方案2
1