【JavaScript】去重

ES6 Set

function unique(arr) {
  return Array.from(new Set(arr))
}
let arr = [1, 2, 3, 4, 5, 1, 2, 3]
console.log(unique(arr))
// [1, 2, 3, 4, 5]

当前项和剩余项比较

function unique(arr) {
  let newArr = []
  for (let i = 0; i < arr.length; i++) {
    let current = arr[i]
    let residue = arr.slice(i + 1)
    if (residue.indexOf(current) === -1) {
      newArr.push(current)
    }
  }
  return newArr
}
let arr = [1, 2, 3, 4, 5, 1, 2, 3]
console.log(unique(arr))
// [4, 5, 1, 2, 3]

先排序，再进行遍历及相邻元素比对去重

function unique(arr) {
  arr.sort((a, b) => a - b)
  let newArr = [arr[0]]
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] !== arr[i - 1]) {
      newArr.push(arr[i])
    }
  }
  return newArr
}
let arr = [1, 2, 3, 4, 5, 1, 2, 3]
console.log(unique(arr))
// [4, 5, 1, 2, 3]

利用对象的属性不能相同的特点进行去重

function unique(arr) {
  let obj = {}
  let newArr = []
  for (let i = 0; i < arr.length; i++) {
    current = arr[i]
    if (!obj[current]) {
      obj[current] = 1
      newArr.push(current)
    }
  }
  return newArr
}
let arr = [1, 2, 3, 4, 5, 1, 2, 3]
console.log(unique(arr))
// [1, 2, 3, 4, 5]

更新完整版：使用 ES6 Map 配合计数排序

function uniq(arr) {
  const map = new Map()
  const len = arr.length

  if (!(arr instanceof Array)) {
    throw new Error(`is not a array!`)
  }

  for (let i = 0; i < len; i++) {
    let temp = arr[i]
    if (!temp) continue
    if (map.has(temp)) continue
    map.set(temp, true)
  }

  return [...map.keys()]
}