HTML文本区域不使用占位符显示

<textarea id="myTextarea" onfocus="clearPlaceholder()" onblur="setPlaceholder()">请输入内容...</textarea>

<script>
function clearPlaceholder() {
  var textarea = document.getElementById("myTextarea");
  if (textarea.value == "请输入内容...") {
    textarea.value = "";
  }
}

function setPlaceholder() {
  var textarea = document.getElementById("myTextarea");
  if (textarea.value == "") {
    textarea.value = "请输入内容...";
  }
}
</script>

<style>
textarea::placeholder {
  color: transparent;
}
</style>

<textarea placeholder="请输入内容..."></textarea>