function(str){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 ;}
原文：http://www.cnblogs.com/xiejunzhao/p/cb50fab9e01446ce9c620275ded60e39.html