数组去重的几种方法

set 方法去重

 let arr = [1, 5, 3, 3, 5]
 console.log([...new Set(arr)])  //  [1, 5, 3]
 console.log(Array.from(new Set(arr))); // [1, 5, 3]
 

双重for循环+ splice()

     let arr = [1, 5, 3, 3, 5]
     for (let i = 0; i < arr.length; i++) {
         for (let j = i + 1; j < i + arr.length; j++) {
             if (arr[i] === arr[j]) {
                 arr.splice(j, 1)
                 j--
             }
         }

     }
 console.log(arr);  // [1, 5, 3]

双重for循环 + 开关思想

  let arr = [1, 5, 3, 3, 5]
   let newArr = []
   for (let i = 0; i < arr.length; i++) {
       let falg = true
       for (let j = 0; j < newArr.length; j++) {
           if (arr[i] === newArr[j]) {
               falg = false
               break
           }
       };
       if (falg) {
           newArr.push(arr[i])
       }
   };
   console.log(newArr);  //   [1, 5, 3]

利用filter() + indexOf()

  let arr = [1, 5, 3, 3, 5]
  const res = arr.filter((item, index) => {
      return arr.indexOf(item) == index
  })
  console.log(res);  // [1, 5, 3]

利用for循环 + indexOf()

      let arr = [1, 5, 3, 3, 5]
      let newArr = []
      for (let i = 0; i < arr.length; i++) {
          if (newArr.indexOf(arr[i]) === -1) {
              newArr.push(arr[i])
          }
      };
      console.log(newArr); // [1, 5, 3]
      

利用 map 数据结构去重

      let arr = [1, 2, 3, 4, 3, 2, 3, 4, 6, 7, 6]
      let unique = (arr) => {
          let seen = new Map()
          return arr.filter((item) => {
              return !seen.has(item) && seen.set(item, 1)
          })
      }
      console.log(unique(arr)); // [1, 2, 3, 4, 6, 7]