JS数组 并集 交集 差集

JS数组 并集 交集 差集

现有两个数组a=[1, 2, 3];b=[2, 4, 5],求数组的并集，交集，合集

• ES5

  //并集
  let union=a.concat(b.filter(item=>a.indexof(item)==-1))//[1,2,3,4,5]
  //交集
  let intersection=a.filter(item=>b.indexOf(item)!==-1)//[2]
  //差集
  let differece=a.filter(item=>b.indexOf(item)==-1).concat(b.filter(item=>a.indexOf(item)==-1))//[1, 3, 4, 5]
  

• Es6

  //并集
  let union=Array.from(new Set([..a,..b]))//[1,2,3,4,5]
  //交集
  let intersection=Array.from(new Set(a.filter(item=>new Set(b).has(item))))
  //差集
  let differece=[...Array.from([...a.filter(item=>!new Set(b).has(item)),...b.filter(item=>!new Set(a).has(item))])]////[1, 3, 4, 5]
  

• Es7

  //并集
  let union=a.concat(b.filter(item=>!a.includes(item)))
  //交集
  let intersection=a.filter(item=?a.includes(item))
  //差集
  let defference=a.concat(b).filter(item=>!a.includes(item)||!b.includes(item))