使用嵌套的 forEach 循环推送到数组

Question

I'd love an explanation as to why the result of this else if statement doesn't match my expectation. my if statement works fine, but else if statement pushes the same value to my array. what I am trying to do is that, if by end of the period person is greater than 18 i want childEndDate to be dates of person date when he/she will become 18 years old.

here is my stackblitz

this.childbirthYear.forEach(element => {
  if (periodEndYear - element < 18) {
    this.childEndDate = this.endDate;
  } else if (periodEndYear - element >= 18) {
    this.childBirthDate.forEach(year => {
      this.childEndDate = addYears(new Date(year), 18).toISOString();
    });
  }
  this.final.push(this.childEndDate);
});
console.log(this.final)

person dates i have now is:

this.childBirthDate = [
  '2012-02-16T20:00:00.000Z',
  '2010-05-19T20:00:00.000Z',
];

array returns

["2028-05-19T20:00:00.000Z", "2028-05-19T20:00:00.000Z"]

but it must return

["2030-05-19T20:00:00.000Z", "2028-05-19T20:00:00.000Z"]

Answer 1

If you want this.childEndDate to hold the year when the person became 18 simply take the element which hold the birthyear and add with 18

dont know why you are using another forEach loop inside the else if

this.childbirthYear.forEach(element => {
  if (periodEndYear - element < 18) {
    this.childEndDate = this.endDate;
  } else if (periodEndYear - element >= 18) {
      this.childEndDate = addYears(new Date(element), 18).toISOString();
  }
  this.final.push(this.childEndDate);
});
console.log(this.final)

Gives output

['2030-01-01T00:00:00.000Z', '2028-01-01T00:00:00.000Z']

Answer 2

I think the following code should do for you...

    const lessThan18s = this.childBirthDate.filter(birthDate => (periodEndYear - new Date(birthDate).getFullYear()) < 18);

    const greaterThan18s = this.childBirthDate
    .filter((birthDate: string) => (periodEndYear - new Date(birthDate).getFullYear()) >= 18)
    .forEach((birthDate: string) => {
       this.final.push(addYears(new Date(birthDate), 18).toISOString());
     });