Скачать или смотреть Setting Default Values with lodash Pick for Missing Keys

Learn how to clean up JavaScript objects by setting default values for missing keys using `lodash`'s `pick` and `defaults` functionalities.
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This video is based on the question https://stackoverflow.com/q/63994402/ asked by the user 'Harshita' ( https://stackoverflow.com/u/6941369/ ) and on the answer https://stackoverflow.com/a/63994543/ provided by the user 'Dmitry Reutov' ( https://stackoverflow.com/u/12150021/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Setting Default Values with lodash Pick for Missing Keys

In JavaScript, working with data structures such as arrays of objects can often require cleaning up and standardizing data. For example, you might have two datasets — one that serves as a template for the expected structure and another that contains varied data, some of which may lack certain keys. A common challenge is to ensure that objects conform to the expected shape while also ensuring that any missing keys are filled in with default values.

In this guide, we will explore how to effectively use Lodash's pick and defaults methods to extract and clean up our data. Let’s dive into how to achieve this with a concrete example!

The Problem

Imagine you have a header array that defines the keys you want to keep:

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

You also have another dataset, resultsArr, which contains user information:

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

From resultsArr, you want to create a new array that:

Contains only the keys defined in header.

Assigns default values to any missing keys.

The expected output should look like this:

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

The Solution

Let’s break down our solution into clear, manageable steps.

1. Convert Header to an Object

First, we need to convert the header array into a single object that combines all the defined keys along with their default values.

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

2. Get the Keys from the Header

Next, we extract the keys from our unified header object. These keys will be used to filter our results.

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

3. Map Through Results and Clean Up

Now we'll map through resultsArr. For each object in the array, we will:

Use _.pick() to select only the keys defined in header.

Combine this with the headerUnified to ensure all keys are present, filling in defaults automatically.

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

Complete Code

Now let’s put it all together:

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

Conclusion

By leveraging Lodash's pick and defaults, we've efficiently transformed our data to ensure it only includes the expected keys, while also filling in any gaps with default values from the header. This method not only streamlines data handling but also establishes consistency across datasets.

Now, next time you face similar challenges, you can easily apply this technique to ensure your data is clean and well-structured!

Happy coding!