三种js数组去重的简洁方案

function removal(arr) {

  return Array.from(new Set(arr))

}

let arr=[1,2,1,3,4,5,5]

removal(arr)//[1, 2, 3, 4]

function removal(arr){

  return arr.filter((item,index,arr)=>{

      return arr.indexOf(item,0) == index;

  })

}

let arr=[1,2,1,3,4,5,5]

removal(arr)//[1, 2, 3, 4]

let newArr = arr.reduce((prev, cur) => {

    prev.indexOf(cur) === -1 && prev.push(cur);

    return prev;

},[]);