判读字符串长度

function len(s) {

            var l = 0;

            var a = s.split("");

            for (var i = 0; i < a.length; i++) {

                if (a[i].charCodeAt(0) < 299) {

                    l++;

                } else {

                    l += 2;

                }

            }

            return l;

        }