About JavaScript Cheat Sheet

Searchable reference: variables, async, classes, DOM, fetch, gotchas, ES2020–2024. Part of the DevTools Surf developer suite. Browse more tools in the JavaScript collection.

Use Cases

• Frontend devs refreshing on modern JS destructuring syntax
• Code reviewers checking if a pattern uses idiomatic ES2020+
• Backend Node.js developers adopting nullish coalescing and optional chaining
• Bootcamp grads building muscle memory for async/await patterns

Tips

• Use the search bar to jump to a specific ES2020+ feature
• Bookmark sections on nullish coalescing for quick reference
• Compare destructuring patterns side by side with examples

Fun Facts

• JavaScript was created by Brendan Eich in just 10 days in May 1995, originally named Mocha, then LiveScript.
• The nullish coalescing operator (??) was officially added in ES2020, solving a decade-old problem with falsy-value checks using ||.
• Optional chaining (?.) was proposed in 2017 but took three years to reach Stage 4 and ship in ES2020.

FAQ

Which ES version does it cover?

ES2020 through ES2024. Top-level await, optional chaining, nullish coalescing, WeakRefs, Array.at(), Object.hasOwn(), structured clone.

Does it explain 'this'?

Yes — the four binding rules and how arrow functions differ. The most-searched JS topic gets its own section.

What about async/await gotchas?

Sequential vs parallel, error handling (try/catch + Promise.all), and the 'async in forEach' anti-pattern.

Is TypeScript covered?

Separate cheatsheet. Use the TypeScript one for type-level content; this covers the JS runtime and syntax.