Javascript tooling
Gatsby offers support for the standard Javascript toolchain.
TypeScript
Gatsby supports TypeScript automatically, with the ability to modify the default configuration if desired. Gatsby also supports GraphQL Typegen.
Bundling and transpilation
Gatsby uses webpack to bundle files and Babel to transpile Javascript.
Most sites work great with the default configuration. Many common changes have Gatsby plugins already which you can install in your gatsby-config.js.
Linting and auto-formatting
Gatsby supports the use of ESLint and Prettier to enforce code styling standards.