2023

(typescript setup, typescript new project, jest, esbuild, repl)

Install deps:

  npm install -g typescript  
  mkdir <my-project>  
  cd <my-project>  
  npm install --save-dev ts-node  
  npm install --save-dev jest  
  npm install --save-dev ts-jest  
  npm install --save-dev @types/jest  
  npm install --save-dev --save-exact esbuild  
  npm install --save-dev tsconfig-paths  

Setup tsconfig.json. See current tsconfig here

  {  
    "compilerOptions": {  
      "allowImportingTsExtensions": true,  
      "baseUrl": ".",  
      "esModuleInterop": true,  
      "isolatedModules": true,  
      "lib": ["es6"],  
      "noEmit": true,  
      "noImplicitAny": true,  
      "noUnusedLocals": true, // Turn this off when using repl  
      "strict": true,  
      "target": "es6",  
      "typeRoots": [  
        "./node_modules/@types",  
      ],  
    }  
  }  

Create jest.config.js with the following contents:

  module.exports = {  
      "roots": [  
        "./test",  
        // I add './src' here so that `npm run watch_test` reruns tests whenever  
        // changes are made to files under the `src` tree.  
        // There are no tests in the `src` tree.  
        "./src",  
      ],  
      "testMatch": [  
        "**/?(*.)+(spec|test).+(ts|tsx|js)"  
      ],  
      "transform": {  
        "^.+\\.(ts|tsx)$": "ts-jest"  
      },  
  }  

Add the following to package.json:

  ...  
  "scripts": {  
    "bundle": "./node_modules/.bin/esbuild main.ts --bundle --outfile=main.js",  
    "repl": "npx ts-node -r tsconfig-paths/register",  
    "test": "jest",  
    "typecheck": "tsc --project tsconfig.json",  
    "watch_bundle": "npm run bundle -- --watch=forever",  
    "watch_test": "npm run test -- --watch",  
    "watch_typecheck": "npm run typecheck -- --watch --preserveWatchOutput"  
  }  

Create project dirs:

  mkdir <project-dir>/src  
  mkdir <project-dir>/test  

Write main.ts:

  // Contents of <my-project>/main.ts  
  import { myFunction } from 'src/dependency.ts'  
  console.log(myFunction())  

Write a source file that main depends on:

  // Contents of <my-project>/src/dependency.ts  
  export function myFunction(): string {  
      return "hello world"  
  }  

Write a test:

  // Contents of <my-project>/test/dependency.test.ts  
  import { myFunction } from '../src/dependency.ts'  

  test("myFunction says hello world", () => {  
     expect(myFunction()).toBe("hello world")  
  })  

Run test with:

  npm run test  

typecheck with:

  npm run typecheck  

bundle with:

  npm run bundle  
  node main.js  
  :: prints 'hello world'  

Start repl with:

  npm run repl  
  > import {myFunction} from 'src/dependency.ts'  
  > myFunction()  
  :: prints 'hello world'