Find all unique values in array and than split it and return something else

Question

My goal is to find all the unique years in this array and than return it as a array. I have almost done it but cant figure out how I will return the split value.

function findUniqueYears() {
  const arr = ['1973-11-01', '2001-01-01', '1999-10-01', '2007-10-01', '2016-06-01', '2005-08-01', '1973-09-01', '1979-12-01', '2001-08-01'];
  for (var i = 0; i < arr.length; i++) {
    for (var j = i + 1; j < arr.length; j++) {
      if (arr[i].split("-")[0] === arr[j].split("-")[0]) {
        arr.splice(j, 1);
      }
    }
  }
  console.log(arr)
}

Answer 1

这应该做

const findUniqueYears = (arr) => Array.from(new Set(arr.map(item => item.split('-')[0])))

Answer 2

You can use the function map to iterate via each element in the array then you can easily split date by '-' return 0 value and cast it to Set.

function findUniqueYears() {
  const arr = ['1973-11-01', '2001-01-01', '1999-10-01', '2007-10-01', '2016-06-01', '2005-08-01', '1973-09-01', '1979-12-01', '2001-08-01'];
  return new Set(arr.map((el) => el.split('-')[0]))
}