转：JS 算某一年的周六周日

 1 function getMonthLength(date) {
 2   let d = new Date(date)
 3   d.setMonth(d.getMonth()+1)
 4   d.setDate('1')
 5   d.setDate(d.getDate()-1)
 6   return d.getDate()
 7 }
 8 
 9 var arr =[]
10 for (var i =1;i<=12;i++ ){
11  var days = getMonthLength(`2021-${i}-01`)
12  for (var j =1;j<=days;j++ ){
13   if(new Date(`2021-${i}-${j}`).getDay() === 0 || new Date(`2021-${i}-${j}`).getDay() === 6){
14    console.log(`2021-${i}-${j}`)
15    arr.push(`2021-${i}-${j}`)
16   }
17  }
18 }

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