Lazy iterator

Creates iterator that iterate over collection lazily

Example:

const iter = require('lazyiter');

function fib(n) {
    return n < 2 ? n : fib(n-2) + fib(n-1);
}

var list = iter([11, 22, 133, 144, 155]);

list.map(fib).take(2).collect() // [ 89, 17711 ]

// and no big CPU consumption, because of laziness

You can pass iterators between functions and add new layers in any moment, and no computation happens until you apply eager method

function foo(arr) {
    // no computation here
    return lazyiter(arr).map(e => e.toUpperCase())
}

var a = foo(["Oleg", "Jeka", "Dimon", "Demian", "Artem", "Escobar"]);

// add new layers

a.take(3).filter(e => e.length < 6)

// compute either with `collect`
a.collect() // [ 'OLEG', 'JEKA', 'DIMON' ]

// or by hand (note: iterator can be traversed only once)
a.next();  // { value: 'OLEG', done: false }
a.next();  // { value: 'JEKA', done: false }
a.next();  // { value: 'DIMON', done: false }
a.next();  // { value: undefined, done: true }

Methods

Lazy:

• map(fn) - return new iterator that apply fn to every entry
• filter(fn) - return new iterator that apply fn to every entry and exlude the entry if fn return false
• takewhile(fn) - return new iterator that apply fn to every entry until fn return false and exclude enries for which fn return false and rest of enries for which fn was not applied
• take(n) - return new iterator that has only first n entries

Eager:

• forEach(fn) - go through enries and apply fn to each entry
• find(fn) - go throuh entries and apply fn for each entry until fn return true, return the entry for which fn return true
• reduce([acc,] fn) - reduce enries with fn
• collect() - convert iterator into array