Set/from/reduce/...arr

1. find the duplicated parts from two arrays

//use 'Set+filter+includes'
let arr1=[1,3,4,5,6,7,8]
let arr2=[2,3,6,8,9]
let arr3=[...new Set(arr1)].filter(item => arr2.includes(item))
console.log(arr3)

2. sum the arrays

let arr=[2,3,4,6,6,5,3,5,6]
let sum=arr.reduce((x,y)=>x+y)
console.log(sum)

3. delete duplicated items

let arr=[1,2,3,2,4,5,4,3,4,5,6]
let arr1=[...new Set(arr)]
let arr2=Array.from(new Set(arr))
console.log(arr1)
console.log(arr2)