转：JS 算某一年的周六周日

function getMonthLength(date) {
  let d = new Date(date)
  d.setMonth(d.getMonth()+1)
  d.setDate('1')
  d.setDate(d.getDate()-1)
  return d.getDate()
}

var arr =[]
for (var i =1;i<=12;i++ ){
 var days = getMonthLength(`2021-${i}-01`)
 for (var j =1;j<=days;j++ ){
  if(new Date(`2021-${i}-${j}`).getDay() === 0 || new Date(`2021-${i}-${j}`).getDay() === 6){
   console.log(`2021-${i}-${j}`)
   arr.push(`2021-${i}-${j}`)
  }
 }
}

转载： https://www.javascriptc.com/interview-tips/zh_cn/javascript/array-multiple-intersections/