方法1：
String.prototype.gblen = function() { ???var len = 0; ???for (var i=0; i<this.length; i++) { ?????if (this.charCodeAt(i)>127 || this.charCodeAt(i)==94) { ????????len += 2; ??????} else { ????????len ++; ??????} ????} ???return len; ?}方法2：
function strlen(str){ ???var len = 0; ???for (var i=0; i<str.length; i++) { ?????var c = str.charCodeAt(i); ????//单字节加1 ?????if ((c >= 0x0001 && c <= 0x007e) || (0xff60<=c && c<=0xff9f)) { ???????len++; ?????} ?????else { ??????len+=2; ?????} ????} ????return len;}方法3：
var jmz = {};jmz.GetLength = function(str) { ?///<summary>获得字符串实际长度，中文2，英文1</summary> ?///<param name="str">要获得长度的字符串</param> ?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; ?} ?return realLength;};方法4：
var l = str.length; var blen = 0; for(i=0; i<l; i++) { if ((str.charCodeAt(i) & 0xff00) != 0) { blen ++; } blen ++; }方法5：
getBLen = function(str) { ?if (str == null) return 0; ?if (typeof str != "string"){ ???str += ""; ?} ?return str.replace(/[^\x00-\xff]/g,"01").length;}js判断字符串长度
原文地址：http://www.cnblogs.com/hello321/p/7821400.html