vue3 displays placeholder after adding contenteditable="true" to div

html:

<div contenteditable="true" class="title_content" :placeholder="placeholder"></div>

js:

let placeholder = ref("点击输入标题");

css:

.title_content:empty:before {
    
    
  content: attr(placeholder);
  font-size: 38px;
  color: #999;
}
.title_content:focus:before {
    
    
  content: "";
}