JavaScript去重

Array.from(new Set(arr))或[...new Set(arr)]：

var arr = [1,1,2,5,6,3,5,5,6,8,9,8];
console.log(Array.from(new Set(arr)))
// console.log([...new Set(arr)])

for循環嵌套，利用splice去重：

function unique (origin) {
  let arr = [].concat(origin);
  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;
}
var arr = [1,1,2,5,6,3,5,5,6,8,9,8];
console.log(unique(arr))

新建數組，利用includes去重:

function unique (arr) {
  let res = []
  for (let i = 0; i < arr.length; i++) {
    if (!res.includes(arr[i])) {
      res.push(arr[i])
    }
  }
  return res;
}
var arr = [1,1,2,5,6,3,5,5,6,8,9,8];
console.log(unique(arr))

先用sort排序，然後用一個指針從第0位開始，配合while循環去重：

function unique (arr) {
  arr = arr.sort(); // 排序之後的數組
  let pointer = 0;
  while (arr[pointer]) {
    if (arr[pointer] != arr[pointer + 1]) { // 若這一項和下一項不相等則指針往下移
      pointer++;
    } else { // 否則刪除下一項
      arr.splice(pointer + 1, 1);
    }
  }
  return arr;
}
var arr = [1,1,2,5,6,3,5,5,6,8,9,8];
console.log(unique(arr))

待補充