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2021-02-06 ~ 2 min read

New typescript yarn project


  • install yarn
  • initialize a project using yarn
  • add dependencies
  • setup a decent tsconfig


desription of yarn

Create an initial package.json, the project configuration file:

$ yarn init

Install initial dependencies (-D flag is a development dependency):

$ yarn add @types/node typescript
$ yarn add -D ts-node

Create tsconfig.json, required for tsc and ts-node, to compile TypeScript to JavaScript:

$ yarn tsc --init --rootDir src --outDir ./bin --esModuleInterop --lib ES2019 --module commonjs --noImplicitAny true

Create your first source file in src folder:

$ mkdir src
$ echo “console.log(‘Hello World\!\!\!)> src/app.ts

Build the project:

$ yarn tsc

tsc, TypeScript to JavaScript compiler, is located in ./node_modules/.bin/tsc. yarn resolves the path and run it with node. The command above compiles our TypeScript to JavaScript with an ouput to ./bin folder. Now, you can run the output JavaScript file, ./bin/app.js, with node:
$ node ./bin/app.js

For development purposes, ts-node is used, to run code without a compilation. ts-node will compile it on fly:

$ yarn ts-node ./src/app.ts

As with tsc, we run ts-node with yarn to resolve it location.

If you really want to set it up properly, you also add nodemon for hot-reloading of the code changes

$ nodemon --watch "src/**" --ext "ts,json" --ignore "src/**/*.spec.ts" --exec "ts-node src/index.ts"

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Hi, I'm Eric. I'm a software engineer and data scientist based in Lisbon. You can follow me on Twitter, see some of my work on GitHub,