代码如下：
<SCRIPT LANGUAGE="JavaScript"> <!-- Begin var str_in; var str_out = ""; var num_in; var num_out = ""; var e = "Enter Text!"; function str_to_num(form) { num_out = ""; if(form.input.value == "") alert(e); else { str_in = escape(form.input.value); for(i = 0; i < str_in.length; i++) { num_out += str_in.charCodeAt(i) - 23; } form.output.value = num_out; form.input.value = ""; } } function num_to_str(form) { str_out = ""; if(form.output.value == "") alert(e) else { num_out = form.output.value; for(i = 0; i < num_out.length; i += 2) { num_in = parseInt(num_out.substr(i,[2])) + 23; num_in = unescape('%' + num_in.toString(16)); str_out += num_in; } form.input.value = unescape(str_out); form.output.value = ""; } } // End --> </script> <center> <form name=encryptform> <table> <tr> <td align=center> <input name=input type=text size=40 value="JavaScript Fairyland"> </td> <td align=center> <input type=button value="<--" onClick="javascript:num_to_str(this.form)"> <br> <input type=button value="-->" onClick="javascript:str_to_num(this.form)"> </td> <td align=center> <input name=output type=text size=40> </td> </tr> </table> </form> </center>