JS 实现 startWith endWith函数

String.prototype.EndWith = function(s) {
                if (s == null || s == "" || this.length == 0
                        || s.length > this.length)
                    return false;
                if (this.substring(this.length - s.length) == s)
                    return true;
                else
                    return false;
                return true;
            }

            String.prototype.StartWith = function(s) {
                if (s == null || s == "" || this.length == 0
                        || s.length > this.length)
                    return false;
                if (this.substr(0, s.length) == s)
                    return true;
                else
                    return false;
                return true;
            }