重複削除

const arr = ['い', 'ろ', 'は', 'に', 'ほ', 'は', 'い', 'ほ', 'へ', 'と'];

// setを使う
const set = new Set(arr);
const newArr = [...set];
// const newArr = Array.from(set);

console.log(set);
console.log(newArr);

// for文を使う
let newArr2 = [];
for (let item of arr) {
  if (!newArr2.includes(item)) {
    newArr2.push(item);
  }
}
console.log(newArr2);

// reduceを使う
const newArr3 = arr.reduce((accu, curr) => {
  return accu.includes(curr) ? accu : [...accu, curr];
}, [])
console.log(newArr3);

// filter
const newArr4 = arr.filter((item, index) => {
  return arr.indexOf(item) === index;
})
console.log(newArr4)