Filtering array of objects by an out of order array of IDs in Javascript

Question

Here's an array of book objects.

const books=[
    {
      "id": 1,
      "title": "NPR",
      "url": "https://www.npr.org"
    },
    {
      "id": 2,
      "title": "Google Docs",
      "url": "https://docs.google.com/"
    },
    {
      "title": "Fetch API Docs",
      "url": "https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch",
      "id": 3
    },
    {
      "title": "Yahoo",
      "url": "http://www.yahoo.com",
      "id": 4
    },
    {
      "title": "Google",
      "url": "http://www.google.com",
      "id": 5
    }
  ]

And a separate array of IDs

const selectedIds = [1, 5, 3]

With javascript, how can I filter the books array to just the selectedIds (keeping the same order as in selectedIds)?

Final result I'm looking to get:

selectedBooks = [
    {
      "id": 1,
      "title": "NPR",
      "url": "https://www.npr.org"
    },
    {
      "title": "Google",
      "url": "http://www.google.com",
      "id": 5
    },
    {
      "title": "Fetch API Docs",
      "url": "https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch",
      "id": 3
    }
  ]

My current code is like this but this preserves the order of the books array (i.e. [1, 3, 5]):

books.filter(function(item) {
   return selectedIds.includes(item.id);
}

You sure you got the incorrect result. I tested your code on Chromium 77.0.3865.90 and Firefox Quantum 69.0.1 (64-bit) and they seemed to give out the correct order. I can only assume that your const selectedIds's order could be changed to 1, 3, 5 to ensure order preservation. NVM that, I read too quickly, you wanted to keep the order of selectedIDs. :) — Kevin Ng
– Kevin Ng, Commented Oct 7, 2019 at 20:01

bryan60 · Accepted Answer · 2019-10-07 19:49:56Z

3

Go in the other direction.

 selectedIds.map(id => books.find(b => b.id === id))

answered Oct 7, 2019 at 19:49

bryan60

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ksav · Accepted Answer · 2019-10-07 19:52:06Z

1

const books = [{
    id: 1,
    title: "NPR",
    url: "https://www.npr.org"
  },
  {
    id: 2,
    title: "Google Docs",
    url: "https://docs.google.com/"
  },
  {
    title: "Fetch API Docs",
    url: "https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch",
    id: 3
  },
  {
    title: "Yahoo",
    url: "http://www.yahoo.com",
    id: 4
  },
  {
    title: "Google",
    url: "http://www.google.com",
    id: 5
  }
];

const selectedIds = [1, 5, 3];

const mapped = selectedIds.map(id => {
  return books.find(book => book.id === id);
});

console.log(mapped);

answered Oct 7, 2019 at 19:52

ksav

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