获取半年前当月的开始时间及当天结束时间

HTMl

<span id="body">你好</span>
<button type="button" >点击</button>

JS

function getWhatDate(str) { //有参数传递为起始时间,无参数传递为结束时间
				// 获取时间戳和数据周期 // 开始时间，格式yyyy - MM - dd HH: mm: ss
				var nowdate = new Date();
				var halfYearDate = new Date(Date.now() - (365 / 2 * 24 * 3600 * 1000));
				if (str) {
					timeDate = getdate(halfYearDate, str)
				} else {
					timeDate = getdate(nowdate)
				}

				function getdate(date, str) {
					// Y = date.getFullYear() + '-';
					// M = (date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1) : date.getMonth() + 1) + '-';
					// D = (date.getDate() < 10 ? '0' + date.getDate() : date.getDate()) + ' ';
					// h = (date.getHours() < 10 ? '0' + date.getHours() : date.getHours()) + ':';
					// m = (date.getMinutes() < 10 ? '0' + date.getMinutes() : date.getMinutes()) + ':';
					// s = date.getSeconds() < 10 ? '0' + date.getSeconds() : date.getSeconds()
					Y = date.getFullYear();
					M = (date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1) : date.getMonth() + 1);
					D = (date.getDate() < 10 ? '0' + date.getDate() : date.getDate());
					h = (date.getHours() < 10 ? '0' + date.getHours() : date.getHours());
					m = (date.getMinutes() < 10 ? '0' + date.getMinutes() : date.getMinutes());
					s = date.getSeconds() < 10 ? '0' + date.getSeconds() : date.getSeconds()
					if (str) {
						if (M <= 11) {
							return Y + '-' + (M + 1) + '-' + '01 00:00:00';
						} else {
							return (Y + 1) + '-' + '01-01 00:00:00';
						}
					} else {
						return Y + '-' + M + '-' + D + ' 23:59:59';
					}
				}
				return timeDate
			}
				$("button").on("click",function(){
				var time = getWhatDate('start')
				var end = getWhatDate()
				console.log(time,end)
			})