1.project initialize

yarn init

2.install typescript to devDependencies (use for typescript transpiler)

yarn add typescript -D

3.install type definitions for Node.js

yarn add @types/node -D

4.create typescript config ("tsc command" is installed in step 2)

tsc -init

5.edit tsconfig.json in project root, key: "rootDirs" is for ".ts" you put the typescript source file, key: "outDir" is for which path you want to put the ".js" file that be transpiled from typescript.

6.enjoy coding with type in javascript! You can test typescript by:

yarn start