以当前时间为基础，便捷获取时间（最近2天，最近1周，最近2周，最近1月，最近2月，最近半年，最近一年，本周，本月，本年）

console.log(day('最近1周'));        

function day(newval) {
                const date = new Date();
                let endTime=formatTime(date);
                let date1 = Date.parse(date);
                let start = '';
                let end = '';
                let oneDay = 1000 * 3600 * 24;

                switch (newval) {
                    case '今天':
                        start = new Date();
                        break;
                    case '最近2天':
                        start = date1 - oneDay * 2;
                        break;
                    case '最近1周':
                        start = date1 - oneDay * 7;
                        break;
                    case '最近2周':
                        start = date1 - oneDay * 14;
                        break;
                    case '最近1月':
                        start = new Date();
                        start.setMonth(start.getMonth() - 1,)
                        break;
                    case '最近2月':
                        start = new Date();
                        start.setMonth(start.getMonth() - 2,)
                        break;
                    case '最近半年':
                        start = date1 - oneDay * 183;
                        break;
                    case '最近一年':
                        start = new Date();
                        start.setYear(start.getFullYear() - 1)
                        break;
                    case '本周':
                        let a = 6 - date.getDay();
                        start = new Date(date1 - oneDay * a).setHours(0, 0, 0, 0);
                        end = new Date(date1 + oneDay * (1 + date.getDay())).setHours(24, 0, 0, 0)
                        break;
                    case '本月':
                        start = new Date();
                        start.setHours(0, 0, 0, 0)
                        start.setMonth(start.getMonth(), 1)
                        end = new Date(start)
                        end.setHours(0, 0, 0, 0)
                        end.setMonth(start.getMonth() + 1, 1)
                        break;
                    case '本年':
                        start = new Date();
                        start.setHours(0, 0, 0, 0)
                        start.setMonth(0, 1)
                        start.setYear(start.getFullYear())
                        end = new Date(start)
                        end.setHours(0, 0, 0, 0)
                        end.setMonth(start.getMonth(), 1)
                        end.setYear(start.getFullYear() + 1)
                        break;
                }

                return {
                    startTime:this.formatTime(new Date(start)),
                    endTime:end ?  this.formatTime(new Date(end)) : endTime ,
                }

            }

  //格式化时间
       function     formatTime(param) {
                let y = param.getFullYear();
                let m = param.getMonth() + 1;
                let d = param.getDate();
                m = m < 10 ? ("0" + m) : m;
                d = d < 10 ? ("0" + d) : d;
                return y + "-" + m + "-" + d + " ";
            }