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immutable-js
Immutable persistent data collections for Javascript which increase efficiency and simplicity.
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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
JavaScript is most programers' first introduction to map, filter, and reduce. Easy lambdas made those higher-order functions a staple of a lot of JS code.
Meanwhile, immutable.js[0] is at 10 million downloads per week and rising.
I would add that it's not just the ease of use of lambdas, but the fact that in JavaScript functions really are first class citizens. Most of the other widely used languages that people start on have lambda functions added in as a bit of a hack and only treat some functions as real values.
[0] https://www.npmjs.com/package/immutable