CODEWITHSUNDEEP
arraysangulartypescript
lona bin
lona bin

Reputation: 25

Return array when use .reduce Angular

The following function does not return an array but only an object element. I do not understand why

  const selectedId = selectedItems.reduce<string[]>(
      (acc, curr, index) => ({
        ...acc,
        item: curr.id
      }),
      []
    );
    console.log('selectedId ', selectedId ); // {"item": "1"}

I want to select an array like this: item: ["1", "2", "3"]

Please any idea, who is a problem in my code?

Upvotes: 1

Views: 35

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074455

It returns an object because it returns whatever the last thing your callback function returned was,¹ and your callback function is returning an object (not an array).

You may have meant to use [] rather than {} for the callback's return value (=> [...acc, item: curr.id]), but if so, that operation is more clearly expressed via map:

const selectedId = selectedItems.map(item => item.id);

(I'd also suggest using the plural — selectedIds — since it holds multiple ID values.)

¹ If you use reduce on an empty array, your callback is never called, and so the seed value you provided is returned instead. (And if you don't provide one, reduce throws an error.)

Upvotes: 1

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