Why Deno?
The Lykn toolchain uses Deno exclusively. The reasons align with Lykn’s own design principles:
ESM-native — all code is ES modules. No require, no CommonJS, no .mjs vs .js. This matches Lykn’s ESM-only compilation (Ch 16).
Single binary — deno is one executable. No npm install for the toolchain. Install Deno, clone lykn, build with cargo — done.
Permissions — network, file, and environment access must be explicitly granted. deno run --allow-read app.js is the minimum. Security by default, not by opt-in.
Built-in tools — test runner, formatter, linter, task runner, and permission model. Lykn wraps the project workflow; Deno supplies the runtime machinery underneath.
Node.js compatibility — Deno runs most Node.js code via node: specifiers (import "node:fs") and npm packages via npm: specifiers. The ecosystem is accessible.
Standard library — jsr:@std/* provides vetted, maintained utilities: HTTP servers, path manipulation, assertions, encoding.
The Daily Workflow
The Lykn developer’s commands:
lykn run packages/my-app/mod.lykn # compile + run
lykn test # compile tests to target/lykn/test/ and run them
lykn build # build workspace packages to target/lykn/build/
lykn lint packages/my-app test # lint Lykn source
deno run --allow-net target/lykn/build/my-app/mod.js # run built JS directly when teaching Deno