document.getElementbyId（）返回null [英] document.getElementbyId() returning null

问题描述

在标记为//错误的行中的代码中。我收到Javascript错误说：无法读取属性样式'null'。我不知道什么是无法找到的对象。我曾考虑过尝试过一切。请帮忙。以下是代码：

In the code at the line marked as //Error in comments. I get Javascript error saying: "Cannot read property style of 'null'". I have no idea what it is not able to find the object. I have thought and tried everything. Please help. Here is the code:

<script type="text/javascript">

    $.getJSON('https://graph.facebook.com/647045111?fields=first_name&<%= Session["Token"] %>',

    function (data) {
        $('#userName').html(data.first_name);
    });

    document.getElementById('connectedUnregistered').style.display = 'block'; //Error

</script>

    <div id="userName"></div>

    <div id="disconnected" style="display:block;">

     <div id="heading">Facebook login</div> 

     <a href="Account/FacebookLogin" id="loginButton"><div id="fbConnectButton"><img src="/Content/Images/fbconnect.png"/></div></a>    

    </div>

     <div id="connectedUnregistered" style="display:none">

     <div id="heading">Register Now</div> 



    </div>

推荐答案

您正在执行您的JavaScript代码， $ c>< div id =connectedUnregistered/> 实际创建。

You are executing your javascript code BEFORE the <div id="connectedUnregistered" /> was actually created.

另请注意，您没有关闭您的< div> 与相应的< / div> 。

Also note that you did not close your <div> with a corresponding </div>.

所以将您的JavaScript代码移动到HTML之下的部分。或者在页面加载完成后执行。如果您使用JQuery，您可以执行以下操作：

So move your javascript code to a part below your HTML. Or execute it after the page finished loading. If you are using JQuery you can do:

<script>

    $(document).ready(function() {

        ... your code ...

    });
</script>

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