JS Array 過濾重覆值的幾種方式

陣列裡 有時後會處理到把重覆的值濾掉，有以下幾種方式

以這個陣列為例

let arr = ['Apple', 'Banana', 'Orange', 'Mango', 'Orange', 'Apple'];

---

filter

function removeRepeat(data) {
  return data.filter((element, index, array) => {
    return array.indexOf(element) === index;
  });
}

console.log(removeRepeat(arr));
// ['Apple', 'Banana', 'Orange', 'Mango']

---

forEach

function removeRepeat(data) {
  let unique = [];
  data.forEach((element) => {
    if (!unique.includes(element)) {
      unique.push(element);
    }
  });
  return unique;
}

console.log(removeRepeat(arr));
// ['Apple', 'Banana', 'Orange', 'Mango']

---

reduce

function removeRepeat(data) {
  let unique = data.reduce((acc, cur) => {
    if (acc.indexOf(cur) < 0) {
      acc.push(cur);
    }
    return acc;
  }, []);
  return unique;
}

console.log(removeRepeat(arr));
// ['Apple', 'Banana', 'Orange', 'Mango']

Set (目前最常用的方式)

function removeRepeat(data) {
  return [...new Set(data)];
}

console.log(removeRepeat(arr));
// ['Apple', 'Banana', 'Orange', 'Mango']

---

map

function removeRepeat(data) {
  let unique = [];
  data.map((element) => {
    if (!unique.includes(element)) {
      unique.push(element);
    }
  });
  return unique;
}

console.log(removeRepeat(arr));
// ['Apple', 'Banana', 'Orange', 'Mango']

以上