[piedar]

Have you seen https://github.com/labs42io/itiriri? It does lazy queries on iterables, like IEnumerable from C#.

    import { query } from 'itiriri';

    function* fibonacci() {
       let [a, b] = [0, 1];

      while (true) {
        yield a;
        [a, b] = [b, a + b];
      }
    }

    // Finding first 3 Fibonacci numbers that contain 42
    const result = query(fibonacci())
      .filter(x => x.toString().indexOf('42') !== -1)
      .take(3);

    for (const e of result) {
      console.log(e);
    }

    // outputs: 514229, 267914296, 7778742049

[dvlsg]

I wrote a lib that does this too. It's been a while, but using generators tended to be way slower than just using arrays, except in the most obvious cases (array of 1000000 elements, only take 5, no sorting involved, etc). Maybe that's changed. It's been a while since I've checked.