super-iterable

super-iterable is a JavaScript library providing ES6 Iterable utilities.

Features

• Utility methods like map and filter for ES6 Iterables
• Lazy evaluation (it's nature of Iterables)
• TypeScript .d.ts included (only for ES6 output mode)

super-iterable itself is written in ES6 and TypeScript.

Examples

Fizzbuzz

import _ from "super-iterable";
 
function fizzbuzz(n) {
  if (n % 15 === 0) {
    return "fizzbuzz";
  } else if (n % 3 === 0) {
    return "fizz";
  } else if (n % 5 === 0) {
    return "buzz";
  } else {
    return n.toString();
  }
}
 
for (const out of _.times(50).map(fizzbuzz)) {
  console.log(out);
}

Fibonacci sequence

const _ = require("super-iterable");
 
const fibs = _(function* () {
  let a = 0;
  let b = 1;
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
});
for (const fib of fibs.take(50)) {
  console.log(fib);
}

Install

npm install --save super-iterable

How to use

// example.js
 
const _ = require("super-iterable");
// or you can do this in Babel
import _ from "super-iterable";
 
// your code...

Babel + Node

If you are using Babel + Node, you have to override ignore option to import super-iterable module as ES6 (Babel ignores JavaScript files inside node_modules by default).

Example:

babel-node --ignore false example.js

TypeScript + ES6

Since super-iterable provides TypeScript type definitions by default, it is also nice to use it in TypeScript.

TypeScript >= 1.8 (nightly) is recommended, since it has started support CommonJS when targeting ES6.

// example.ts
import _ = require("super-iterable");
 
// your code...

API

_(iterable) => SuperIterable

Wraps an Iterable into a SuperIterable.

// arrays
_([1,2,3]) //=> SuperIterable(1,2,3)
 
// sets
const set = new Set([1,2,3]);
_(set); //=> SuperIterable(1,2,3)
 
// maps
const map = new Map([1, "one"], [2, "two"]);
_(map); //=> SuperIterable([1, "one"], [2, "two"])

_(generatorFunc) => SuperIterable

Creates a SuperIterable from a generator function.

_(function *() {
  yield 1;
  yield 2;
  yield 3;
}); //=> SuperIterable(1,2,3)

_.times(count)

Creates a SuperIterable that enumerates 0 .. count.

_.times(3)
  .toArray(); //=> [0,1,2]

_.count(begin, step = 1)

Creates a SuperIterable that enumerates begin, begin + step, begin + 2 *step ... .

_.count(1, 2)
  .take(3)
  .toArray(); //=> [1,3,5]

SuperIterable

SuperIterable is a convenient wrapper for Iterable objects. SuperIterable itself is also an Iterable.

SuperIterable#map(func)

Transforms values with func function.

_([1,2,3])
  .map(x => x * 2)
  .toArray(); //=> [2,4,6]

SuperIterable#filter(pred)

Filters values with pred function.

_([1,2,3,4])
  .filter(x => x % 2 == 0)
  .toArray(); //=> [2,4]

SuperIterable#flatMap(func)

Transforms values into Iterables with func function and concatenates them.

_([1,2,3])
  .flatMap(x => [x, x * 2])
  .toArray(); //=> [1,2,2,4,3,6]

SuperIterable#entries(func)

Make pairs from the indices and the values.

_(["foo", "bar", "baz"])
  .entries(); //=> [[1, "foo"], [2, "bar"], [3, "baz"]]

SuperIterable#reduce(func, initValue)

Accumulates each value.

_([1,2,3,4])
  .reduce((acc, x) => acc * x, 1); //=> 24

SuperIterable#take(count)

Takes the first count values.

_(["foo", "bar", "baz"])
  .take(2); //=> ["foo", "bar"]

SuperIterable#takeWhile(pred)

Takes the elements while pred(element) is true.

_([2,4,6,5,4])
  .takeWhile(x => x % 2 == 0); //=> [2,4,6]

SuperIterable#drop(count)

Drops the first count values.

_([1,2,3,1,2])
  .drop(2); //=> [3,1,2]

SuperIterable#dropWhile(pred)

Drops the elements while pred(element) is true.

_([2,4,6,5,4])
  .dropWhile(x => x % 2 == 0); //=> [5,4]

SuperIterable#count()

Counts the elements.

_([1,2,3,4])
  .count(); //=> 4

SuperIterable#concat(...otherIterables)

Concatenates Iterables.

_([1,2,3,4])
  .concat([5,6,7], new Set([8,9])); //=> [1,2,3,4,5,6,7,8,9]

SuperIterable#every(pred)

Returns true if every elements fulfills pred condition, otherwise false.

_([2,4,6])
  .every(x => x % 2 == 0); //=> true

_([1,2,3])
  .every(x => x % 2 == 0); //=> false

SuperIterable#some(pred)

Returns true if at least one element fulfills pred condition, otherwise false.

_([1,2,3])
  .some(x => x % 2 == 0); //=> true

_([1,3,5])
  .some(x => x % 2 == 0); //=> false

SuperIterable#find(pred)

Returns the element that fulfills pred condition, otherwise undefined.

_([1,4,3])
  .find(x => x % 2 == 0); //=> 4

_([1,5,3])
  .find(x => x % 2 == 0); //=> undefined

SuperIterable#findIndex(predicate)

Returns the index of the element that fulfills pred condition, otherwise -1.

_([1,4,3])
  .find(x => x % 2 == 0); //=> 1

_([1,5,3])
  .find(x => x % 2 == 0); //=> -1

SuperIterable#indexOf(elem)

Returns the index of the element, or returns -1 if it is not found.

_([1,4,3])
  .indexOf(4); // => 1

_([1,5,3])
  .indexOf(4); // => -1

SuperIterable#includes(elem)

Returns whether the SuperIterable includes the element or not.

_([1,4,3])
  .includes(4); // => true

_([1,5,3])
  .includes(4); // => false

SuperIterable#keys()

Returns the "keys" (the first values of element pairs).

_([[1,2],[3,4],[5,6]])
  .keys(); //=> [1,3,5]

SuperIterable#values()

Returns the "values" (the second values of element pairs).

_([[1,2],[3,4],[5,6]])
  .keys(); //=> [2,4,6]

SuperIterable#toArray()

Converts the SuperIterable into an Array.

_([1,2,3,4])
  .toArray(); //=> [1,2,3,4]