效果：例如你输入的为"你们好好好好"，截取之后是"你们好好好"，数字和字母就直接是10位了，如果是"你们好11111111"，截取之后是"你们好1111",希望对大家有帮助。。。
<script type="text/javascript"> function Count(text, long) { var strlen=""; var str = document.getElementById('TextBox1').value; var realLength = 0, len = str.length, charCode = -1; for (var i = 0; i < len; i++) { charCode = str.charCodeAt(i); if (charCode >= 0 && charCode <= 128) realLength += 1; else realLength += 2; } var maxlength = new Number(long); // Change number to your max length. if (realLength > maxlength) { for (var i = 0; i <len; i++) { strleg=str.substring(0,i); for(var j=0;j<=10;j++) { charCode1 = strleg.charCodeAt(j); if (charCode1 >= 0 && charCode1 <= 128) j += 1; else j += 2; } if(j==Number(10))break; } text.value =strleg; //text.value.substring(0, maxlength); alert(maxlength); } } </script> <body> <form runat="server"> <div> <asp:TextBox ID="TextBox1" runat="server" onKeyUp="javascript:Count(this,10);" onChange="javascript:Count(this,10);"></asp:TextBox> </div> </form></body>
