js日期格式化函数&&日期加减

Date.prototype.format = function (fmt) {
    var year = this.getFullYear();
    var month = this.getMonth() + 1;
    var date = this.getDate();

    fmt = fmt.replace("yyyy", year);
    fmt = fmt.replace("yy", year % 100);
    fmt = fmt.replace("MM", fix(month));
    fmt = fmt.replace("dd", fix(this.getDate()));
    fmt = fmt.replace("HH", fix(this.getHours()));
    fmt = fmt.replace("mm", fix(this.getMinutes()));
    fmt = fmt.replace("ss", fix(this.getSeconds()));
    return fmt;
    function fix(n) {
        return n < 10 ? "0" + n : n;
    }
}

 使用：
var date1 = new Date(selectedDate);
var newDate = new Date(date1.getTime() + 24 * 60 * 60 * 1000); //加一天
var newDateStr = newDate.format("yyyy-MM-dd");
$("#txtDay2").val(newDateStr);