javascript - 用js填充textarea

Question

我不明白为什么这不起作用:(

<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>

Answer 1

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

<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>