javascript - 无法读取 null 的属性 'focus'

Question

我试图专注于输入窗口，但它给出错误:

<div class="intercom-conversation-footer" data-
    reactid=".2.1.$=1$conversation.2"><div class="intercom-composer" data-
    reactid=".2.1.$=1$conversation.2.0"><pre data-
    reactid=".2.1.$=1$conversation.2.0.0"><span data-
    reactid=".2.1.$=1$conversation.2.0.0.0">write something</span><br data-
    reactid=".2.1.$=1$conversation.2.0.0.1"></pre><textarea placeholder="Write 
    a reply..." data-reactid=".2.1.$=1$conversation.2.0.1"> </textarea><span
     data-reactid=".2.1.$=1$conversation.2.0.2"></span><button class="intercom-
    composer-emoji-button" data-reactid=".2.1.$=1$conversation.2.0.5"></button>
    <button class="intercom-composer-send-button" data-
    reactid=".2.1.$=1$conversation.2.0.7"></button></div></div>

我想专注于此，我该怎么做？

我的代码是:

var message = document.createEvent("TextEvent");  
message.initTextEvent ("textInput", true, true, window, "Hello", 0, "en-US");
document.getElementById(".2.1.$=1$conversation.2.0.0.0").focus();

但它给出错误:

VM20681:1 Uncaught TypeError: Cannot read property 'focus' of null(…)

Answer 1

你没有 id，只有 data-reactid 属性。因此，您可以使用类似的内容:document.querySelector("span[data-reactid='.2.1.$=1$conversation.2.0.0.0']").focus();