map return undefined array of object?

Question

const newDate = map(items.result, (obj => {
  if (isDateWithinRage(obj.date_from)) {
    return {
      "date": obj.join_date,
      "name": obj.student.name
    }
  }
}))

The if statement has produced something like this

[Object, Object, Object, Object, Object, undefined, undefined, undefined, undefined, Object, Object, Object]

How to fix the undefined part? I want to skip the iteration.

I think you are looking for filter developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Maxwelll
– Maxwelll, Commented Apr 25, 2017 at 4:12

zzzzBov · Accepted Answer · 2017-04-25 04:15:54Z

3

Assuming map is some variant of Array.prototype.map, map produces a 1:1 mapping of values from your input array to an output array.

When you want to exclude values from your input array, use Array.prototype.filter:

const newDate =
  items
    .result
    .filter(obj => isDateWithinRange(obj.date_from))
    .map(obj => ({
      date: obj.join_date,
      name: obj.student.name
    }));

_{This example assumes that items.result is an Array}

answered Apr 25, 2017 at 4:15

zzzzBov

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