如何让Textarea的每一行都有一个占位符文本

<textarea id="myTextarea" rows="5" placeholder="请输入内容"></textarea>

var textarea = document.getElementById("myTextarea");

textarea.addEventListener("input", function() {
  var lines = textarea.value.split("\n");
  var placeholderText = "占位符文本";

  for (var i = 0; i < lines.length; i++) {
    if (lines[i] === "") {
      lines[i] = placeholderText;
    }
  }

  textarea.value = lines.join("\n");
});