Getting Started

jetl is a data processing library for JavaScript built on top of asynchronous iterators.

It is written in TypeScript and compiles to pure JavaScript, meaning that it can be used in both server and browser environments.

Quick Start

This example processes an array of integer numbers by:

• filtering out the odd numbers
• increasing each remaining number by 1
• computing their sum

The example is editable so you can play around with it

Live Editor

const result = new pipeline() .add([1, 2, 3, 4, 5, 6]) .add(filter(n => n % 2 === 0)) .add(map(n => n + 1)) .add(apply(reduce((acc, c) => acc + c, 0))) .run() // 2, 4, 6 => 3, 5, 7 // 3 + 5 + 7 => 15 return `Sum: ${await first(result)}`

const result = new pipeline()
  .add([1, 2, 3, 4, 5, 6])
  .add(filter(n => n % 2 === 0))
  .add(map(n => n + 1))
  .add(apply(reduce((acc, c) => acc + c, 0)))
  .run()

// 2, 4, 6 => 3, 5, 7
// 3 + 5 + 7 => 15
return `Sum: ${await first(result)}`

Result

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How it works

1. [1, 2, 3, 4, 5, 6] provides the initial data source to the pipeline as an array of numbers
2. filter(n => n % 2 === 0) adds an operation which filters only the even numbers
3. map(n => n + 1) transforms each element by incrementing it by 1
4. apply(reduce((acc, c) => acc + c, 0)) applies an operator which, given the transformed array of numbers, turns it into the sum of those numbers
5. .run() executes the pipeline and returns an asynchronously iterable of results
6. await first(result) asynchronously returns the first element of the result

Concepts

In the example above:

• new pipeline() creates a new pipeline
• filter, map, apply are operations. Operations are functions which accept iterables as inputs and return iterables as output
• reduce and first are operator. Operators are functions which accept iterables as input and can return anything (including scalar values)