Question

我不明白为什么这不起作用:(

＆＃13;

<textarea class="js-compose-text compose-text txt-size--14 scroll-v scroll-styled-v scroll-styled-h scroll-alt padding-a--0" placeholder="What's happening?" style="height: 130px;"></textarea>
<button type="button" onclick="myFunction()">Try it</button>
<script>
function myFunction() {
  document.getElementsByClassName("js-compose-text compose-text txt-size--14 scroll-v scroll-styled-v scroll-styled-h scroll-alt padding-a--0").value = "TESTESTTEST";
}

</script>

＆＃13;

Answer 1

getElementsByClassName返回一个类似数组的对象，因此您需要指定document.getElementsByClassName("js-compose-text compose-text txt-size--14 scroll-v scroll-styled-v scroll-styled-h scroll-alt padding-a--0")[0].value = "TESTESTTEST";

这样的确切元素

＆＃13;

<textarea class="js-compose-text compose-text txt-size--14 scroll-v scroll-styled-v scroll-styled-h scroll-alt padding-a--0" placeholder="What's happening?" style="height: 130px;"></textarea>
<button type="button" onclick="myFunction()">Try it</button>
<script>
function myFunction() {
  document.getElementsByClassName("js-compose-text compose-text txt-size--14 scroll-v scroll-styled-v scroll-styled-h scroll-alt padding-a--0")[0].value = "TESTESTTEST";
}

</script>

＆＃13;

Answer 2

在javascript中，多个textarea或div可以具有相同的类名，但具有唯一的ID＆＃39; s。当你通过它的id访问任何元素时，它是唯一的，你可以通过它的Id调用它，但是当你按名称访问元素时，你必须按索引访问相同类名下的每个元素，如下所述 -

<textarea class="text" id="1"></textarea> //First textarea <textarea class="text" id="2"></textarea> //Second textarea <textarea class="text" id="3"></textarea> //Third textarea <textarea class="text" id="4"></textarea> //Fourth textarea

访问第3个文本区域 -

document.getElementById("3"); //OR document.getElementsByClassName("text")[2];

两个代码都会做同样的事情

用js填充textarea

2 个答案: