用js写数组去重，用5中方法

1. 使用Set数据结构

const arr = [1, 2, 2, 3, 4, 4, 5];
const newArr = [...new Set(arr)];
console.log(newArr); // [1, 2, 3, 4, 5]

2. 使用for循环和indexOf方法

const arr = [1, 2, 2, 3, 4, 4, 5];
const newArr = [];
for (let i = 0; i < arr.length; i++) {
  if (newArr.indexOf(arr[i]) === -1) {
    newArr.push(arr[i]);
  }
}
console.log(newArr); // [1, 2, 3, 4, 5]

3. 使用for循环和includes方法

const arr = [1, 2, 2, 3, 4, 4, 5];
const newArr = [];
for (let i = 0; i < arr.length; i++) {
  if (!newArr.includes(arr[i])) {
    newArr.push(arr[i]);
  }
}
console.log(newArr); // [1, 2, 3, 4, 5]

4. 使用filter方法

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

5. 使用reduce方法

const arr = [1, 2, 2, 3, 4, 4, 5];
const newArr = arr.reduce((prev, curr) => {
  if (!prev.includes(curr)) {
    prev.push(curr);
  }
  return prev;
}, []);
console.log(newArr); // [1, 2, 3, 4, 5]