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Extracting Values from a Nested Array of Objects in JavaScript

Learn how to filter and extract specific values from a nested array of objects in JavaScript easily and efficiently. --- This video is based on the question https://stackoverflow.com/q/68939150/ asked by the user 'Shiny' ( https://stackoverflow.com/u/12003907/ ) and on the answer https://stackoverflow.com/a/68939239/ 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. 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: Extracting values from array nested inside array of objects in javscript 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. --- Extracting Values from a Nested Array of Objects in JavaScript When working with complex data structures in JavaScript, you may encounter situations where you need to extract specific pieces of information from nested arrays. In this post, we'll address a common problem: how to filter out certain objects from an array nested inside array of objects. We’ll walk through an example and provide a clear solution using JavaScript's powerful array methods. The Problem Imagine you have an array of objects, each containing a name and a nested values array, which in turn holds several objects. Your goal is to filter the nested values to only include those with a specific property—specifically, where the name is PASS. Here’s the data structure we'll work with: [[See Video to Reveal this Text or Code Snippet]] From this dataset, we want to create a new object that looks like this: [[See Video to Reveal this Text or Code Snippet]] The Mistake You might try to achieve this by iterating through the objects and values using methods like map() and possibly nesting another map(), but the structure of your code might not yield the desired results. Here's an incorrect attempt: [[See Video to Reveal this Text or Code Snippet]] Key Issues: Using push on an object: You're trying to use push, which is a method for arrays, on an object. Incorrect object property shorthand: You can't directly use {item.name: registry.name.value} to create an object in JavaScript. The Solution The efficient approach is to use the flatMap() method, which allows you to iterate through the parent array and flatten the results of the mapping operation. Here is a working solution: [[See Video to Reveal this Text or Code Snippet]] How It Works: flatMap(): This method is used to map each element using a mapping function (in this case, the filtered values) and then flattens the result into a new array. Filtering Pass Values: The filter() method goes through each object's values to include only those with a name of PASS. Mapping to New Structure: After filtering, map() is used to create the new object structure containing only the name from the parent object and the value from the nested object. Final Output Running the code will yield the following output: [[See Video to Reveal this Text or Code Snippet]] Conclusion Working with nested arrays in JavaScript may seem daunting at first, but with the right methods like flatMap() and a good understanding of how to filter and map, you can efficiently extract the data you need. Don't hesitate to leverage these powerful tools to make your data manipulation tasks simpler and more readable. Happy coding!