yastream

Yet another stream library

Motivation

The use of streams is growing in so many languages, but JavaScript is still lacking this functionality natively.

You might say: "But javascript already has .map, .filter and many other functionalities over arrays." Don't get me wrong, it is enough for several use cases, but consider the following example:

[1, 2, 3, 4]
  .map(value => value * 2)
  .find(element => element > 2)
// expected output: 4

In this case, even though the result comes from the second position of the array, the map iterated all entries before trying to find the right element.

I believe that out there already exists many libraries that do this, but I decided to do my own version in order to learn more about JavaScript.

Installation

This module is distributed via npm:

npm install yastream

Stream operations

Everything begins when you create a stream: stream(array).

There are several operation you can perform over a stream, but some can be stacked and others are terminal. In order to solve the stream it is mandatory to perform a terminal operation

Stackable

• map(map_function)
• filter(condition)

Terminal

• do()
• count()
• reduce(reducer_function, acc_start_value)
• findFirst(condition)

Examples

For quick examples you can check bellow, but for complete functionality coverage you can look into the test files.

Map and filter array

const { stream } = require("yastream")

const result =
    stream([1, 2, 3])
        .map(value => value * 2)
        .filter(value => value > 3)
        .do();
// expected result = [4, 6]

Map, filter and find in array

const { stream } = require("yastream")

const result =
    stream([1, 2, 3])
        .map(value => value * 2)
        .filter(value => value > 3)
        .findFirst(value => value == 4);
// expected result = '4'
// it only iterates the first two element of the array