Question 212926 in Javascript Question posted in
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Javascript – Determine the difference between values in object and array

I have the following object and array of numbers. How can I tell which number in the array does not exist as an id in the object? In the following example, I would want 1453.

[
  {id: 60, itemName: 'Main Location - 1100 Superior Road - Cleveland'}
  {id: 1456, itemName: 'Third Location - 107,West 20th Street,Manhattan - New York'}
]

[60, 1453, 1456]
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3

Answers


  1. 0

    You could create an IDs list of the existing data IDs using .map(), and then use .filter() and .includes()

    const data = [
  {id: 60, itemName: 'Main Location - 1100 Superior Road - Cleveland'},
  {id: 1456, itemName: 'Third Location - 107,West 20th Street,Manhattan - New York'}
]

const ids = [60, 1453, 1456];
const dataIDs = data.map(ob => ob.id);  // [60, 1456]
const notExistentIDs = ids.filter(id => !dataIDs.includes(id));

console.log(notExistentIDs);  // [1453]

    which will return an Array of all the Object IDs (from data) not listed in your reference ids Array.

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  2. 0

    @Roko’s solution is absolutely correct and probably a lot faster. Here’s my alternative approach using .reduce() and .some():

    const data = [
  { id: 60, itemName: "Main Location - 1100 Superior Road - Cleveland" },
  { id: 1456, itemName: "Third Location - 107,West 20th Street,Manhattan - New York" }
];
const ids = [60, 1453, 1456];

const result = ids.reduce(
  (acc, curr) =>
  data.some(d => d.id === curr) ? acc : [...acc, curr], []
);

console.log(result);
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  3. 0

    For a grater amount of data-items and a grater amount of ids I would choose an approach which creates a Set based lookup via mapping each of an itemList item’s id…

    const idLookup = new Set(itemList.map(({ id }) => id));

    Looking up items directly from a Set or a Map instance is much faster than e.g. iterating again and again an array via find or includes for each iteration step of an outer filter task.

    Filtering a list of non matching item-ids then is as straightforward as …

    const listOfNonMatchingIds = idList.filter(id => !idLookup.has(id));

    … example code …

    const itemList = [
  { id: 60, itemName: 'Main Location - 1100 Superior Road - Cleveland' },
  { id: 1456, itemName: 'Third Location - 107,West 20th Street,Manhattan - New York' },
];
const idList = [60, 1453, 1456];

const idLookup = new Set(itemList.map(({ id }) => id));
const listOfNonMatchingIds = idList.filter(id => !idLookup.has(id));

console.log({ listOfNonMatchingIds });
    .as-console-wrapper { min-height: 100%!important; top: 0; }
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