Скачать или смотреть Understanding Object Hash in JavaScript to Remove Duplicates from Arrays

Discover how to effectively use `object hashes` in JavaScript to construct unique arrays by removing duplicates with practical examples and clear explanations.
---
This video is based on the question https://stackoverflow.com/q/62542441/ asked by the user 'kittu' ( https://stackoverflow.com/u/1800583/ ) and on the answer https://stackoverflow.com/a/62542479/ provided by the user 'Unmitigated' ( https://stackoverflow.com/u/9513184/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How object hash works to remove duplicates in this scenario?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Object Hash in JavaScript to Remove Duplicates from Arrays

In the world of programming, dealing with duplicates in array data structures can be a common problem. JavaScript provides an efficient solution through the use of object hashes to ensure that we only keep unique values when merging arrays. In this post, we will explore how the hash method works and clarify how it helps in removing duplicates from merged arrays.

The Problem: Merging Arrays with Duplicates

When you have two arrays and you want to combine them into a single array containing only unique elements, it can get tricky if both arrays contain repeating values. For instance, consider the following two arrays:

[[See Video to Reveal this Text or Code Snippet]]

Here, both arr and arr2 contain several duplicate values. We want to merge these arrays and maintain only the unique values.

The Solution: Using Object Hash for Unique Values

The solution to our problem lies in the distinctUnion function that uses an object as a hash map. Let's look at how this works step-by-step.

Merging the Arrays

Firstly, we merge both arrays into a single array:

[[See Video to Reveal this Text or Code Snippet]]

Now, merged contains all elements from both arrays, including the duplicates.

Implementing the Hash Map

The core part of our solution is the hash map, which is an empty object initialized as the variable map:

[[See Video to Reveal this Text or Code Snippet]]

This object will store each unique value we find while iterating through the merged array.

Iterating and Checking for Uniqueness

Next, we will iterate through each element in the merged array. For every element, we check if it already exists in our hash map:

[[See Video to Reveal this Text or Code Snippet]]

Adding Unique Values to the Result

If merged[i] does not exist in map, it means this value is unique so far. Here's where the magic happens:

[[See Video to Reveal this Text or Code Snippet]]

By adding this key-value pair to our hash map (map[merged[i]] = true;), we’re essentially marking this value as seen. We then push this unique element into the result array.

Complete Code Example

Here is the complete function integrating all the above steps:

[[See Video to Reveal this Text or Code Snippet]]

Demonstrating with Example Output

Running the above code will yield the output with unique values:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion: The Power of Object Hashes

Using an object to track whether we have seen a value before is a powerful technique. It allows us to ensure we only push unique values to the results, efficiently solving the problem of duplicates during array merging. The approach discussed here can be applied in various scenarios where uniqueness is paramount.

By mastering this along with your JavaScript skills, you can confidently handle duplicates in arrays, leading to cleaner and more reliable code.