js 中获得 字符串 的字符长度

function getLength(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;}