How to Update Arrays of Objects in Firestore Without Overwriting the Entire Array?

Updating Arrays of Objects with Firestore

In Firestore, updating arrays of objects can be a complex task. Here, we tackle the issue and provide a solution that resolves the challenges faced in merging data.

The Problem

Typically, modifying arrays in Firestore requires replacing the entire array. Using the SET method overwrites the array, while the UPDATE method performs the same action. This behavior poses limitations when attempting to update individual elements within an array of objects.

The Solution

Firestore now offers two methods for managing arrays without overwriting the entire array:

• arrayUnion(): Adds elements to an array, ensuring that only unique elements are included.
• arrayRemove(): Removes all instances of specified elements from an array.

To update an array of objects using these methods, follow these steps:

1. Reference the document containing the array to update.
2. Use the update() method with either arrayUnion() or arrayRemove().
3. Pass an object to the arrayUnion() method with the updated elements as properties.
4. Pass an array to the arrayRemove() method with the elements to be removed.

Example Code

<code class="javascript">// Add an element to the "sharedWith" array
firebase.firestore()
  .collection('proprietary')
  .doc(docID)
  .update({
    sharedWith: firebase.firestore.FieldValue.arrayUnion({ who: "[email protected]", when: new Date() })
  });

// Remove an element from the "sharedWith" array
firebase.firestore()
  .collection('proprietary')
  .doc(docID)
  .update({
    sharedWith: firebase.firestore.FieldValue.arrayRemove({ who: "[email protected]", when: timestamp })
  });</code>

By utilizing arrayUnion() and arrayRemove(), you can seamlessly update arrays of objects in Firestore, ensuring that changes are merged into the existing array without overwriting it.

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