js 获取指定年份的每月起始年月日

const year = new Date(form.yearly_plan).getFullYear();
 let year_list = []
 for (let i = 1; i < 13; i++) {const end = new Date(year, i, 0).getDate();const m = `0${i}`.slice(-2);year_list.push({`${year}-${m}-0${1}`,`${year}-${m}-${end}`,});
 }