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Cover image for Quick tip: using flatMap() to extract data from a huge set without having to write a loop
Christian Heilmann
Christian Heilmann

Posted on • Updated on • Originally published at christianheilmann.com

Quick tip: using flatMap() to extract data from a huge set without having to write a loop

I just created a massive dataset of all the AI generated metadata of the videos of the WeAreDeveloper World Congress" and I wanted to extract only the tags.

The dataset is a huge array with each item containing a description, generated title, an array of tags, the original and their title, like this:

{
  "description": "The talk begins with an introduction to Twilio…", 
  "generatedtitle: "Enhancing Developer Experience: Strategies ",
  "tags": ["Twilio", "DeveloperExperience", "CognitiveJourney"],
  "title": "Diving into Developer Experience"
}
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What I wanted was an alphabetical lost of all the tags in the whole dataset, and this is a one-liner if you use flatMap():

data.flatMap(d => d.tags);
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You can sort them alphabetically with sort():

data.flatMap(d => d.tags).sort();
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And you can de-dupe the data and only get unique tags when you use Set():

new Set(data.flatMap(d => d.tags).sort());
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You can try this in this codepen.

Top comments (2)

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ahmetcetin profile image
Ahmet Cetin

Who will tell Christian that flatMap is actually a loop? :)

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