Add join operators

[andres-kovalev]

concat(...streams) to add each next stream to the end of previous one

concat([1,2,3], [4,5,6]) => [1,2,3,4,5,6]

merge(...steams) to take items one by one from each stream to build new stream

merge([1,2,3], [4,5,6]) => [1,4,2,5,3,6]

combine(combineFn, ...streams) to create new stream where each item is calculated using according items from source streams

const add = (a,b) => a + b;
combine(add, [1,2,3], [4,5,6]) => [5,7,9]

zip(...streams) creates an array of arrays using combine() under the hood

zip([1,2,3], [4,5,6]) => [[1,4], [2,5], [3,6]];

// equivalent to
combine((...args) => args, [1,2,3], [4,5,6]);