Utilizing Rxjs' distinct operator to perform deep object comparisons with nested values

Within my observable, I am receiving a JSON object and using the distinct operator to avoid duplicates. The challenge is that I want to prevent duplicates only if the entire object remains the same as before. Since comparing based on a single attribute such as id may not be sufficient due to varying content.

Currently, my workaround is to stringify the object before applying the distinct operator, which has been effective so far.

Do you know of a more efficient method to achieve this?

someObservable
  .startWith(cachedCopy)
  .map(item => JSON.stringify(item))
  .distinct()
  .subscribe(item => {
      //Some instructions here!
     })

Answer №1

In my opinion, the most straightforward approach to comparing if two objects contain the same data is by utilizing JSON.stringify(). If you are certain that the object identities must be different, then you could consider using

pairwise().filter(pair => pair[0] !== pair[1])
(ensuring they are distinct object instances). However, this approach is highly dependent on your specific use-case and whether such a condition can be guaranteed (which has rarely been the case in my personal experience as comparing JSONs usually suffices).

It's important to note that distinct() only passes through truly distinct items created within the chain. Given your explanation stating "duplicates if the entire object is the same as before", it appears that distinctUntilChanged would be more appropriate for your scenario.

The distinctUntilChanged operator allows an optional comparator function parameter to assess if two objects are identical:

.distinctUntilChanged((prev, curr) => JSON.stringify(prev) === JSON.stringify(curr))

Answer №2

Utilizing lodash within your application provides the opportunity to easily make use of the isEqual() function, allowing for a deep comparison that aligns perfectly with the signature of distinctUntilChanged():

.distinctUntilChanged(isEqual),

Alternatively, if you still have access to _ (although it is no longer recommended in current times):

.distinctUntilChanged(_.isEqual),

Answer №3

I decided to utilize the Underscore.js Library, specifically its 'unique' function which proved to be a lifesaver for me. https://underscorejs.org/#uniq

1- First step is to install it:

$ npm install underscore

2- Then, make sure to call it in your code:

import { _ } from 'underscore';

3- Finally, you can use it by simply implementing the following line of code:

this.allcate = _.uniq(this.allcate);

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