iteragain

iteragain

Another Javascript library for iterating.

Pure JavaScript, ES6 Iterable/Iterator utilities. No dependencies and shipped with types as is.

Inspired by iterplus, iterare and the Python itertools module. See benchmark section for performance.

The package is designed around the use of the ExtendedIterator class. It's a class that extends the ES6 Iterator with methods like those in 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, etc.

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

Benchmark

Starting benchmark suite: index.bm.ts
  for of loop 10000 x 1,198 ops/sec, ±35 ops/sec or ±2.94% (88 runs sampled)
  iteragain 10000 x 856 ops/sec, ±14 ops/sec or ±1.67% (89 runs sampled)
  iterare 10000 x 747 ops/sec, ±13 ops/sec or ±1.77% (92 runs sampled)
  iterplus 10000 x 547 ops/sec, ±8 ops/sec or ±1.43% (92 runs sampled)
Fastest is for of loop 10000