JS find function pushing undefined

Question

I created a "filter" function that receives an array of objects. Each object has an accountId property. My function is supposed to filter out objects that have a different accountId. It is, however, pushing an undefined object in there.

What's wrong with my function?

export const filterItems = (myArray, accountId) => {

   let filteredItems = [];
   filteredItems.push(myArray.find(items => items.accountId === accountId));

   return filteredItems;
}

When I pass an accountId to my function that is not in the array, the output is an array with one item in it and the item is undefined -- see below:

[
  0: undefined
]

What am I doing wrong?

Answer 1

You could just filter the array and return an empty array if not found.

export const filterItems = (myArray, accountId) =>
    myArray.filter(items => items.accountId === accountId);

Answer 2

Your code always calls .push(). The .find() function returns undefined if the item isn't found.

You can grab the return value from .find() and then only push the result when it's actually found:

let filteredItems = [];
let item = myArray.find(items => items.accountId === accountId);
if (item !== undefined)
  filteredItems.push(item);
return filteredItems;

Answer 3

myArray.find(items => items.accountId === accountId) is returning undefined (and it is being pushed to filteredItems)

Try this instead:

//...
let item = myArray.find(items => items.accountId === accountId);

if(item) {
    filteredItems.push(item);
}
//...