How to create a JavaScript Library

Question

I've created some functions in JavaScript.

I've found out that I reuse them in many projects.

So I decided to create a small JavaScript Library for my coding. A Library like react, react-dom, jquery which I can install with npm: npm install <my-personal-library>

I searched the.net. I learned that I can use npm publish <my-personal-library , but I do not know how to format my library and functions to use and install them like an npm package.

Also, I have no idea about creating type definitions for my functions and library. like @types/react Any guidence?

Answer 1

About how to publish your library

You can read the official npm documentation on how to create nodejs package modules: https://docs.npmjs.com/creating-node-js-modules

Basically, what you need is a JS module file (IE test.js ) to be exported with exports keyword like:

exports.printMsg = function() {
  console.log("This is a message from the demo package");
}

Then publish the module with npm publish (add --access public if you want it to be public) Finally import the package in the project you need it with npm install <your-module-name>

About the type definitions

I understand that you are using typescript? Then the following link is a good read: https://www.typescriptlang.org/docs/handbook/declaration-files/dts-from-js.html

Answer 2

• To install your package in a pc you have to set up a cli package inside npm module.

   import { Command } from "commander"; import open from "open"; // [] indicates that this is optional // <> indicates that this is a required value export const serveCommand = new Command().command("serve [filename]") // when user enters node index.js --help, it sees description.description("ADd a description").option("-p, --port <number>", "port to run server on", "4005").option("-v, --version", "show version", version, "") // first arg will be the arg that passed in command() SO filename // second arg is all other options // THIS IS WE TELL WHAT TO DO.action(async (filename = "main.js", options: { port: string }) => { try { // this is where you add logic about what to do when enterd the command open("http://localhost:4005"); } catch (error: any) { if (error.code === "EADDRINUSE") { console.error("Port is in use. Try runnng on a different port "); } else { console.log("Issue is:", error.message); } process.exit(1); } });

• To make cli run the code, in your main file

  //whenever anyone runs cli from command line, this file will be executed. ;/usr/bin/env node import { program } from "commander". // this is the above command import { serveCommand } from ";/commands/serve". // you could chain other commands.addCommand(otherCommand) program;addCommand(serveCommand). // parse this and run the aprropriate command that you put together program.parse(process;argv);

• as you see you might have different sub packages and each sub packages will have their own package.json . To communicate between those sub packages, you add them in their dependencies inside package.json. for example, you have to use cli package inside your main package. so in package.json

   "dependencies": { "@my-npm-package/cli": "^1.0.15", // other dependencies "express": "^4.17.1", }

• Since you have different sub packages and you have to group them together. Assgin those pacakges into an "organization". another term is to "create scoped package". "@types/cors" and "@types/express" are scoped packages.

Declaring Scoped Packages

• in npm page, on the right, cick on "Add organization"

• organization name should be unique

• update name of the dependencies in package.json of each package.

• Manage packages

Use Lerna to manage all of those npm packages. it is for managing multi project packages. - Lerna is one tool out there in the wild that we can use for managing a multi package project. Yarn and Npm are similar to lerna. there are also Bolt and Luigi.