数组去重

function removeDup(arr){
  const ret = []
  for(let i = 0; i < arr.length; i ++){
    if(ret.indexOf(arr[i]) < 0){
      ret.push(arr[i])
    }
  }
  return ret
}

function Uniq(arr = []) {
    return arr.reduce((t, v) => t.includes(v) ? t : [...t, v], []);
}

Array.from(new Set(arr))

[...new Set(arr)]