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Runtime Basics

deno run permissions model --allow-read --allow-write --allow-net --allow-env permission prompts Deno.version Deno.args environment variables

Modules

ES module imports URL imports npm imports jsr imports import maps deno.json imports local modules dynamic import top-level await module caching

File & Process APIs

Deno.readTextFile Deno.writeTextFile Deno.open Deno.readDir Deno.stat Deno.mkdir Deno.remove Deno.Command process output

HTTP

Deno.serve request URL parsing request headers request body JSON responses status codes redirect responses streaming responses server abort signal WebSocket upgrade

Tooling

deno fmt deno lint deno check deno test test steps assertions benchmarks deno task deno doc deno info

Dependencies & Packaging

deno add lockfile vendor dependencies npm compatibility Node built-ins package.json support workspaces deno compile deno install executable publishing to JSR

Web APIs

fetch AbortController URL and URLSearchParams Web Crypto TextEncoder TextDecoder ReadableStream WritableStream BroadcastChannel Web Workers timers

Production & Security

least-privilege permissions permission scoped paths permission scoped hosts TLS certificates secrets via environment structured logging graceful shutdown error boundaries resource cleanup deployment checklist

Deno / Modules

module caching

Learn module caching in Deno with a dedicated explanation, a topic-specific example, edge guidance, and a mastery check.

12 min read • Beginner

deno-020.ts

typescript

import "./initialize.ts";
import "./initialize.ts";
// The same module is evaluated once per module graph.

What to watch

Content source & attribution

Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

module caching Mastery Check →

top-level await

Deno.readTextFile