用法：obj.labels代表该元素所绑定的标签元素所构成的集合 <body> <script> function checkVal(){ var txtName=document.getElementById("txt_name"); var form=document.getElementById("testform"); var btn=document.getElementById("btn"); if(txtName.value.trim()=="") { //trim()意思为去掉两边空格 var label = document.createElement("label"); label.setAttribute("for","txt_name"); form.insertBefore(label, btn); txtName.labels[1].innerHTML = "请输入你的姓名"; txtName.labels[1].setAttribute("style", "font-size:14px;color:red;"); }else if(txtName.labels.length>1){ form.removeChild(txtName.labels[1]); } } </script> <form id="testform"> <label id="label" for="txt_name">姓名：</label> <input type="text" id="txt_name"> <input type="button" id="btn" value="验证" οnclick="checkVal()"> </form> </body>