数组去重的几种方法

方法一、双重 for 循环

let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]

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--
    }
  }
}
console.log(arr)
// [1, 2, 3, 4, 6, 7]

方法二、使用 es6 中 Set 方法

let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]

let unique = arr => [...new Set(arr)]
console.log(unique(arr)) // [1, 2, 3, 4, 6, 7]

方法三、定义新数组，用 filter 方法结合 indexOf

let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]

let newArr = []
let result = arr.filter(item => {
  if (newArr.indexOf(item) === -1) return newArr.push(item)
})
console.log(result)
// [1, 2, 3, 4, 6, 7]

方法四、用 filter 方法结合 indexOf

let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]

function unipore(arr) {
   return arr.filter((item, index) => arr.indexOf(item) === index)
}
console.log(unipore(arr))
// [1, 2, 3, 4, 6, 7]

方法五、用 filter 方法结合 includes 方法

let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]

let newArr = []
let result = arr.filter(item => {
   if (!newArr.includes(item)) return newArr.push(item)
})
console.log(result)
// [1, 2, 3, 4, 6, 7]