iteragain

iteragain

Another Javascript library for iterating.

Pure JavaScript, Iterable/Iterator/Generator-function utilities. No dependencies and shipped with types as is.

The package is designed around the use of the ExtendedIterator class through calling iter. It's a class that implements and extends the IterableIterator interface. It provides extra methods like those in the JS Array and other iterator methods in Python. It's chainable and looks closely like normal Javascript code instead of the more Python itertools way of doing things: filter(lambda x: x % 2 == 0, map(lambda x: x * x, iterable))

There is also other utility functions like range, enumerate, zip etc.

See documentation.

Code demo

// Import from the root index
import { iter } from 'iteragain';
// Or from the file itself (tree shakable):
import iter from 'iteragain/iter';
const nums = iter([1, 2, 3])
  .map(n => n * n)
  .filter(n => n % 2 === 0)
  .toArray();
  // [1, 4, 9]

import range from 'iteragain/range';
range(10).toArray(); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
range(10, 0).toArray(); // [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
range(0, -10).toArray(); // [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
range(0, 10, 2).toArray(); // [0, 2, 4, 6, 8]
let r = range(0, 10, 2);
r.length; // 10, (a readonly property)
r.includes(4); // true
r.nth(-1); // 8 (the last element)
r.nth(1); // 2 (the second element)
r.nth(10); // undefined (the 10th element doesn't exist)
r.index(4); // 2 (the index of the value 4)
r = range(3);
const nums = [...r, ...r]; // [0, 1, 2, 0, 1, 2], can be reused after a full iteration.

Inpired by

iterplus, iterare, lodash, rxjs and the Python itertools module. See benchmark section for performance against some of these.

Benchmark

Starting benchmark suite: index.bm.ts
  for of loop x 2,015 ops/sec, ±47 ops/sec or ±2.33% (90 runs sampled)
  iteragain x 1,431 ops/sec, ±25 ops/sec or ±1.74% (92 runs sampled)
  iterare x 1,368 ops/sec, ±20 ops/sec or ±1.48% (95 runs sampled)
  rxjs x 989 ops/sec, ±10 ops/sec or ±1.05% (93 runs sampled)