javascript 计算中文字符长度

function getLength(str) {
        var len = str.length;
        var reLen = 0;
        for (var i = 0; i < len; i++) {
            if (str.charCodeAt(i) < 27 || str.charCodeAt(i) > 126) {
                // 全角
                reLen += 2;
            } else {
                reLen++;
            }
        }
        return reLen;
    }