利用ES6 Set去重

const arr = [1, 2, 3, 4, 4, 5, 6, 6, 7];
const uniqueArr = Array.from(new Set(arr));
// 或者使用扩展运算符
// const uniqueArr = [...new Set(arr)];
console.log(uniqueArr); // [1, 2, 3, 4, 5, 6, 7]

const arr = [1, 2, 3, 4, 4, 5, 6, 6, 7];
const uniqueArr = [];
arr.forEach(item => {
  if (uniqueArr.indexOf(item) === -1) {
    uniqueArr.push(item);
  }
});
console.log(uniqueArr); // [1, 2, 3, 4, 5, 6, 7]

const arr = [1, 2, 3, 4, 4, 5, 6, 6, 7];
const uniqueArr = [];
arr.forEach(item => {
  if (!uniqueArr.includes(item)) {
    uniqueArr.push(item);
  }
});
console.log(uniqueArr); // [1, 2, 3, 4, 5, 6, 7]

const arr = [1, 2, 3, 4, 4, 5, 6, 6, 7];
const uniqueArr = arr.filter((item, index, array) => {
  return array.indexOf(item) === index;
});
console.log(uniqueArr); // [1, 2, 3, 4, 5, 6, 7]

const arr = [1, 2, 3, 4, 4, 5, 6, 6, 7];
const uniqueArr = arr.reduce((result, current) => {
  if (!result.includes(current)) {
    result.push(current);
  }
  return result;
}, []);
console.log(uniqueArr); // [1, 2, 3, 4, 5, 6, 7]