Скачать или смотреть How to Use lodash to Count Array Lengths by Grouping

Discover how to effectively utilize `lodash` to group and count lengths of arrays with this easy-to-follow guide.
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This video is based on the question https://stackoverflow.com/q/62280878/ asked by the user 'sansSpoon' ( https://stackoverflow.com/u/1682405/ ) and on the answer https://stackoverflow.com/a/62281228/ provided by the user 'Ori Drori' ( https://stackoverflow.com/u/5157454/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering Array Grouping with lodash

When working with arrays of objects in JavaScript, one common problem that developers encounter is the need to group items by certain properties and then retrieve counts of those groups. If you’ve found yourself facing this issue, you’re not alone! In this guide, we will explore how to use lodash, a powerful JavaScript utility library, to group an array of objects and count the occurrences of each group.

The Challenge: Grouping and Counting

Imagine you have the following array of objects:

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Upon using lodash to group this array by the type property, you might achieve an output like this:

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Your Goal

What if you want to transform that output to show just the count of each type instead of the full grouped array? For instance, you want to get this result:

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The Solution: Utilizing lodash Functions

Using _.countBy()

Fortunately, lodash provides an elegant solution with the _.countBy() method. This method will count the occurrences of each element based on a specified property. Here’s how you can achieve the desired count in one simple step:

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Using _.mapValues() and _.groupBy()

If you prefer to use _.groupBy() and then calculate the lengths of each group, you can achieve the same outcome by following these steps:

Group the Array: Use _.groupBy() to group objects by their type.

Map Values to Lengths: Use _.mapValues() combined with _.size() to get the length of each grouped array.

Here's the code that implements this method:

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Importing lodash

Don’t forget to include lodash in your HTML for the above methods to work! You can add it like this:

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Conclusion

In summary, lodash provides us with powerful tools for manipulating arrays in a clear and efficient manner. Whether you utilize _.countBy() for direct counting or the combination of _.groupBy() and _.mapValues() for more flexibility, mastering these functions will streamline your data processing tasks in JavaScript.

Now, you should be equipped to tackle any array counting challenge with ease using lodash! Happy coding!