ES6数组去重

使用filter和indexof

const arr = [26, 27, 26, 26, 28, 28, 29, 29, 30]
const uniqArr = arr.filter((value, index, self) => self.indexOf(value) == index )

使用Set

const arr = [26, 27, 26, 26, 28, 28, 29, 29, 30]
const uniqArr = [...new Set(arr)]

or

const arr = [26, 27, 26, 26, 28, 28, 29, 29, 30]
const uniqArr = Array.from(new Set(arr))

Prototype

Array.prototype.unique = function() {
  let arr = [];
  for(let i = 0; i < this.length; i++) {
      if(!arr.includes(this[i])) {
          arr.push(this[i]);
      }
  }
  return arr; 
}

const arr = [26, 27, 26, 26, 28, 28, 29, 29, 30]
const uniqueArr = arr.unique()