What is lazy.js?

Lazy.js is a JavaScript utility library for working with arrays and collections. It is designed for developers who want clean, readable code that also runs efficiently. Traditional libraries like Underscore and Lodash process each step in a chain immediately, creating temporary arrays at every stage. If you ask for the first five results from a list of ten thousand items, they do the work on all ten thousand before trimming down to five. Lazy.js takes a different approach. Instead of executing each operation right away and storing intermediate results, it queues the operations into a sequence and only does the actual work when you request output. That means if you need just five matching items, it stops as soon as it finds them rather than scanning the whole dataset. The API is intentionally kept close to Underscore and Lodash, so the syntax will look familiar to anyone who has used those libraries. Every step in a chain looks the same, the difference is under the hood. The library can also generate indefinite sequences, meaning you can describe a potentially endless series of values, such as random numbers or a Fibonacci sequence, and pull only as many results as you need. This is not possible with array-based libraries that require a fixed input collection to start. For browser environments, an optional extension adds support for treating DOM events as sequences. Mouse movement, key presses, and other events can be filtered, mapped, and transformed using the same methods you would use on an array. There is also string processing support, so operations like splitting a large block of text can stop early rather than generating every line or substring upfront. Lazy.js has no external dependencies and can be installed via npm or included directly in a webpage with a script tag. It is aimed at JavaScript developers working with large datasets or repeated operations who want readable functional code without the performance cost of unnecessary intermediate steps.