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Raphael MANSUY
Raphael MANSUY

Posted on • Originally published at elitizon.com on

How to create and publish a typescript module on npmjs.com

#node #npm #typescript #testing

This tutorial explains

  • How to configure a typescript package from zero
  • How to add the support of Jest for the unit tests
  • How to generate the tests coverage
  • How to publish the library in npmjs.com

Let's create a simple library to validate emails and IPv4 addresses. The name of this library will be xanthe.

️Xanthe means “golden” or “yellow” in Greek. Xanthe is an exotic epithet of Demeter, goddess of the harvest and agriculture 🇬🇷🧚‍♀

Create a package.json file 

{
  "name": "xanthe",
  "version": "0.0.1",
  "author": {
    "email": "contact@elitizon.com",
    "name": "elitizon"
  },
  "license": "MIT",
  "description": "A library to validate common formats such as emails, numbers, phone numbers, and IP addresses",
  "contributors": [
    "raphaelmansuy"
  ],
  "keywords": [
    "format",
    "validator",
    "email validation",
    "IP address validation"
  ],
  "dependencies": {},
  "devDependencies": {}
}
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Install typescript as a development dependencies 

yarn add -D typescript @types/node
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@types/node contains type definitions for Node.js
typescript contains the typescript compiler

Create the src and test directory 

mkdir src
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mkdir tests
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Install a testing environment

Install Jest as a development dependency

Jest is a testing library developed by Facebook.

yarn add -D jest ts-jest
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Create a jest.config.js file to configure Jest 

module.exports = {
  transform: {'^.+\\.ts?$': 'ts-jest'},
  testEnvironment: 'node',
  testRegex: '/tests/.*\\.(test|spec)?\\.(ts|tsx)$',
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node']
}
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  • All the files ending by .ts will be handled by ts-jest.
  • The test environment is nodejs
  • The test files are contained in the ./tests directory and must have .test. or .spec. in the filename and must end by .ts or .tsx

Create a script section in the package.json file 

  "scripts": {
    "build": "tsc",
    "test": "yarn build && jest",
    "coverage": "jest --coverage"
  },
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  • build: invoke the typescript transpiler
  • test: build and invoke the tests
  • coverage: generate the tests coverage in the coverage directory

Create a tsconfig.json file to configure typescript 

{
  "compilerOptions": {
    "target": "es5" ,
    "module": "commonjs",
    "outDir": "./build",
    "strict": true,
    "esModuleInterop": true ,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "declaration": true
  },
  "exclude": ["node_modules", "build", "tests"]
}
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The build command will generate the CommonJS files in the ./build/ directory

Creation of validations functions

Create a file email.ts in ./src/validators/ directory 


/**
 * @param email to validate. No spaces or tab are allowed at the start or at the end of the string
 * @returns true of false if the email is valid or not
 */
function isEmail(email: string) : boolean {
  // An email address is a word followed by an unique @ followed by a word then a . followed by a word with a length of 2 to 3 characters
  const regEx = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/
  const result = regEx.test(email)
  return result
}


export {
  isEmail
}
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Create a file ipV4.js in ./src/validators/ directory 


/**
 * @param ip to validate. (No spaces or tab are allowed at the start or at the end of the string)
 * @returns true of false if the IP is valid or not
 */
function isIPv4(ip: string) : boolean {
  // An ip V4 address has the form of X.X.X.X
  // Where X is a number between 0 to 255
  const regEx = /^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/
  const result = regEx.test(ip)
  return result
}


export {
  isIPv4
}
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Create a file index.ts in ./src/ 

import { isEmail } from "./validators/email"
import { isIPv4 } from "./validators/ipv4"

export { isEmail, isIPv4 }
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Our module is now nearly ready. Let's create the unit tests.

Creation of unit tests

Create an email.test.ts in ./src/tests directory 

import { isEmail } from "../src/index"

test("email luc@perdu.com valid", () => {
  expect(isEmail("luc@perdu.com")).toBe(true)
})

test("Empty string not valid", () => {
  expect(isEmail("")).toBe(false)
})

test("No double @ in an email", () => {
  expect(isEmail("martin@toto@titi.com")).toBe(false)
})

test("not trimmed email to be false", () => {
  expect(isEmail(" luc@perdu.com ")).toBe(false)
})
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Create the ipV4.test.ts in ./src/tests/ directory 

import { isIPv4 } from "../src"

test("192.168.0.1 is valid", () => {

    expect(isIPv4("192.168.0.1")).toBe(true)
})

test("1920.168.0.1 is not valid", () => {

  expect(isIPv4("1920.168.0.1")).toBe(false)
})

test("192.1682.0.1 is not valid", () => {

  expect(isIPv4("192.1682.0.1")).toBe(false)
})

test("192.168.256.1 is not valid", () => {

  expect(isIPv4("192.168.256.1")).toBe(false)
})

test("192.168.255.500 is not valid", () => {

  expect(isIPv4("192.168.255.500")).toBe(false)
})

test("192.168.255.255 is valid", () => {
  expect(isIPv4("192.168.255.255")).toBe(true)
})

test("192.168.X.255 is valid", () => {
  expect(isIPv4("192.168.X.255")).toBe(false)
})
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Let's compile and tests 

yarn build
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yarn test
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Execute the tests coverage 

yarn coverage
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A coverage has been generated with all the information about the tests coverage

Creation of git repository

Create of a .gitignore file 

node_modules
build
coverage
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run git init 

git init
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add the files 

git *
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commit the files 

git commit -m "First commit"
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Publish the file to a Github repository

An empty Github project must be created before publishing.

The file package.json need to be updated as follow:

  "repository": {
    "url": "https://github.com/myorganisation/xanthe.git",
    "type": ""
  },
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myorganisation represents your Github account

We can now set up the Github project as a remote representation of the local project and push the local master branch to the remote server (origin).

git remote add origin`https://github.com/myorganisation/xanthe.git
git branch -M master
git push -u origin master
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Publish to npmjs.org

An account must be created before publishing a package in the npm registry.

  • Once the account is created you need to log into 
npm login
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  • Enter your username, password, and email address registered on npmjs.org

  • Add a new file .npmignore to exclude some files from the publication

README.md
TUTORIAL.md
jest.config.json
tests/
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  • We can now publish it to the library at npmjs.org 
yarn publish
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A few questions will be asked such as the new version number 0.0.1

And "voilà". Our components are published and visible 🥳

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