数组去重的几种方法

记录一些数组去重的方法，如果有错误的地方，还望指正

1.利用es6中的Set()去重特性

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   return [...new Set(arr)]
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

2.利用includes或者indexOf

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   const temp = []
   arr.forEach(item => {
     return temp.includes(item) ? '' : temp.push(item)
   })
   return temp
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

3.暴力双循环

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   const temp = []
   for(let i  = 0; i < arr.length; i++) {
       let repeat = false
       for (let j  = 0; j < temp.length; j++) {
           if (arr[i] === temp[j]) {
              repeat = true
              break
           }
       }

       if(!repeat) {
          temp.push(arr[i])
       }
    }
    return temp
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

4.排序后，前一个和后一个比较，不相同就放入数组

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   const temp = []
   const sortArr = arr.sort()
   for(let i  = 0; i < sortArr.length; i++) {
      if (sortArr[i] !== sortArr[i+1]) {
         temp.push(sortArr[i])
      }
   }
   return temp
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

5.splice改变原数组

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   for(let i = 0; i < arr.length; i++) {
      for(let j = i+1; j < arr.length; j++) {
         if (arr[i] === arr[j]) {
            arr.splice(j, 1)
               j--
         }
      }
    }
    return arr
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

6.利用对象 速度快但是耗费内存

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   const temp = []
   const obj = {}
   for(let i = 0; i < arr.length; i++) {
      if (!obj[arr[i]]) {
         obj[arr[i]] = true
         temp.push(arr[i])
      }
   }
   return temp
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

7.利用reduce

const arr = [1,2,3,6,8,2,9,5,6,4,9]
function uniq(arr) {
   return arr.reduce((pre, cur, arr1) => pre.includes(cur) ? pre : [...pre,cur], [])
}
const resultArr1 = uniq(arr)
console.log(resultArr1)

8.使用filter

function uniq(array) {
    return array.filter((item, index, arr1) => {
    return arr1.indexOf(item) === index
  })
}