Language: TypeScript

I program in JavaScript, because I value isomorphic code (using the same code on the client and the server), being able to implement server-side rendering more easily, and programming in only one language in general. In terms of flavor, I prefer TypeScript (93% satisfaction) over vanilla ES6, because static typing catches a lot of bugs before they happen.

Might change soon?

Very Unlikely

Setup#

TypeScript is automatically configured by Next, but we need to install it as a dev dependency:

Yarn
NPM

yarn add -D typescript

I also often end up installing ts-node to execute TS files, or ts-node-dev to restart the Node process on file changes while developing, both in transpile-only mode.

I also set an absolute path for imports:

"compilerOptions": {
  "baseUrl": "src",
  "paths": {
    "#/*": ["*"]
  },
  // ...
}

Which allows me to import files this way:

import Header from '#/components/Header'

Pick whatever symbol you like. A lot of people use @/ but I find it confusing because scoped packages also start with @.

It is natively supported by Next, but if you are not using Next, you might need tsconfig-paths to get those paths to work with Node, ts-node, and ts-node-dev:

"scripts": {
  "with-node": "node -r tsconfig-paths/register main.js",
  "with-ts-node": "ts-node -r tsconfig-paths/register main.ts",
  "with-ts-node-dev": "tsnd --respawn -r tsconfig-paths/register main.ts"
}

Note: If ts-node is used in production, it should have the --transpile-only flag.

I also set module to commonjs for a broader compatibility with NPM modules:

"compilerOptions": {
  "module": "commonjs",
  // ...
}

Alternatives#

I find TypeScript more reliable than Flow, and it has a much bigger community and support. I would recommend Python to someone learning the fundamentals of programming though.