Context Managers In Javascript

Managing Resources

The usage of resources like file operations or database connections is very common in many programming languages. However, these resources are very limited in supply. Therefore, the main problem lies in making sure to release these resources after usage. If they are not released then it will lead to resource leakage and may cause the system to slow down or even crash. It would be very helpful if developers have a mechanism for automatic setup and teardown of resources.

This pattern can be implemented in Javascript by using contextmanagers. They facilitate the proper handling of resources.

Contextmanagers are similar to contextmanagers in python programming language; in fact, contextlib is a javascript implentation of python contextmanagers.

A simple contextmanager

class Manager {
    enter() {
        console.log("setting up...");
    }
    exit() {
        console.log("cleaning up...")
    }
}

With(new Manager(), () => {
    console.log("inside context");
    throw Error("💔");
})

Output

setting up...
inside context
cleaning up...
Uncaught Error: 💔
    at REPL16:3:11
    at With (/home/blvckphish/projects/contextlib/dist/cjs/with.js:47:21)

Contextmanagers prove to be really useful for different purposes, like;

Automatically handling setup and cleanup.
Managing unreliable code.
Writing clear and concise code.
Preventing errors from bubbling.

Getting Started

Read the developer guide on how to use contextmanagers in your project.

Installing From NPM

The latest version of contextlib can be downloaded via npm

npm install contextlib
```js
const { With } = require("contextlib");

Cloning From Github

The stable release of contextlib would be available on the main branch. The dev branch may contain code that isn't fully tested.

git clone https://github.com/mcsavvy/contextlib.git
cd contextlib

const { With } = require(".");

Contributing