JavaScript 中求出两个数组的交集和差集

        var a = [1,2,3,4]
        var b = [3,4,5,6]
        es6
        let intersection = a.filter(v => b.includes(v))
        let difference = a.concat(b).filter(v => !a.includes(v) || !b.includes(v))

        var intersection = a.filter(function(v){
          return b.indexOf(v)!==-1
        }) 
        var difference = a.concat(b).filter(function(v){
          return a.indexOf(v)===-1 || b.indexOf(v)===-1
        })