演示示例，注意：readonly 区分大小写。
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <TITLE>文本框读写切换</TITLE> <META NAME="Generator" CONTENT="EditPlus"> <META NAME="Author" CONTENT=""> <META NAME="Keywords" CONTENT=""> <META NAME="Description" CONTENT=""> </HEAD> <BODY> <input type="text" id="aa"> <input type="button" onclick="javascript:a();" value="writer"> <input type="button" onclick="javascript:b();" value="readonly"> <script type="text/javascript"> function a(){ document.getElementById("aa").removeAttribute("readOnly"); } function b(){ document.getElementById("aa").setAttribute("readOnly","true"); } </script> </body> </html>