JavaScript Cheat Sheets
Short, printable references for modern JavaScript and the tools around it. Each cheat sheet has its own page with every snippet ready to copy, plus a free PDF to keep next to your editor.
JavaScript Essentials
JavaScript Cheat Sheet
Variables, types, strings, arrays, objects, functions, classes, modules, and async basics.
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JavaScript for Pythonistas Cheat Sheet
Python-to-JavaScript equivalents for None and null, numbers, f-strings, collections, truthiness, loops, classes, exceptions, async, modules, and common traps.
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Array and Iterator Methods Cheat Sheet
Map, filter, reduce, find, some, every, flat, non-mutating methods like toSorted and with, Object.groupBy, Array.from ranges, iterator helpers, and generators.
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Async JavaScript Cheat Sheet
The event loop, promises, async/await, Promise combinators, error handling, fetch, AbortController, and async iteration.
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JavaScript DOM Cheat Sheet
querySelector, addEventListener and event delegation, classList, creating elements, forms and FormData, localStorage, and fetch from the browser.
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JavaScript Gotchas Cheat Sheet
Loose equality, typeof null, NaN, floating-point math, sort(), this binding, hoisting, reference equality, semicolon insertion, parseInt, for...in on arrays, string concatenation, Date months, shallow freeze, and array holes.
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JavaScript Regex Cheat Sheet
Regex literals, flags, character classes, named groups, lookarounds, match and replace methods, RegExp.escape, and lastIndex gotchas.
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TypeScript Cheat Sheet
Type annotations and inference, interfaces vs. type aliases, unions and narrowing, generics, utility types, unknown and satisfies, tsconfig essentials, and running TypeScript in Node.js.
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Node.js Files and Paths Cheat Sheet
Paths with node:path, reading and writing text and JSON, listing and globbing, copying and deleting, file metadata, streams and pipeline, watch mode, and --env-file.
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What's New in JavaScript (ES2026) Cheat Sheet
Map upsert, JSON.parse source text, Iterator.concat, Array.fromAsync, Base64 and hex bytes, Error.isError, and an ES2025 recap.
View Cheat Sheet »npm and Security
npm and package.json Cheat Sheet
npm install and scripts, semver ranges, lock files and npm ci, ESM versus CommonJS, package.json metadata, and pnpm and Bun equivalents.
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npm Supply Chain Security Cheat Sheet
Lockfiles, install scripts, audits, dependency cooldowns, provenance, Trusted Publishing, incident response, and AI agent guardrails.
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JavaScript Security Checklist Cheat Sheet
XSS and textContent, eval, prototype pollution, input validation with zod, secrets and env vars, node:crypto, CSP, CORS, and safe child processes.
View Cheat Sheet »Developer Tools
Git Cheat Sheet
Setup, staging and commits, .gitignore, branches and merging, remotes, stash, and undoing mistakes.
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Claude Code Cheat Sheet
Install and launch flags, headless mode, slash commands, shortcuts, CLAUDE.md, permissions, hooks, skills, subagents, and MCP.
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Claude Code Hooks Cheat Sheet
Hook anatomy, lifecycle events, reading the event payload, exit codes, auto-formatting, notifications, and JSON replies.
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LLM APIs and MCP in JavaScript Cheat Sheet
Claude API calls in Node.js, streaming, tool use, structured output, retries, and building MCP servers and clients.
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