js获取当前时间的前一个月时间

getMonth() {
          const end = new Date();
          const start = new Date();
          start.setTime(start.getTime() - 3600 * 1000 * 24 * 30);
          this.dateRange = [parseTime(start,'{y}{m}{d}'),parseTime(end,'{y}{m}{d}')]
          console.log(this.dateRange);
          this.getList();
        }

// 日期格式化
export function parseTime(time, pattern) {
	if (arguments.length === 0 || !time) {
		return null
	}
	const format = pattern || '{y}-{m}-{d} {h}:{i}:{s}'
	let date
	if (typeof time === 'object') {
		date = time
	} else {
		if ((typeof time === 'string') && (/^[0-9]+$/.test(time))) {
			time = parseInt(time)
		} else if (typeof time === 'string') {
			time = time.replace(new RegExp(/-/gm), '/');
		}
		if ((typeof time === 'number') && (time.toString().length === 10)) {
			time = time * 1000
		}
		date = new Date(time)
	}
	const formatObj = {
		y: date.getFullYear(),
		m: date.getMonth() + 1,
		d: date.getDate(),
		h: date.getHours(),
		i: date.getMinutes(),
		s: date.getSeconds(),
		a: date.getDay()
	}
	const time_str = format.replace(/{(y|m|d|h|i|s|a)+}/g, (result, key) => {
		let value = formatObj[key]
		// Note: getDay() returns 0 on Sunday
		if (key === 'a') { return ['日', '一', '二', '三', '四', '五', '六'][value] }
		if (result.length > 0 && value < 10) {
			value = '0' + value
		}
		return value || 0
	})
	return time_str
}