Cheat Sheets

JavaScript Cheat Sheet

Quick reference for JavaScript — variables, types, functions, arrays, objects, classes, promises, async/await, and the Fetch API.

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Dynamic. Async. Everywhere.

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Variables & Types

letconstvartypeofnull vs undefinedTemplate literals

Operators

ArithmeticStrict equalityLoose equalityLogical AND / ORNullish coalescing (??)Optional chaining (?.)TernarySpread (...)Destructuring

Strings

lengthtoUpperCase / toLowerCasetrim()includes()startsWith / endsWithslice()replace()split()padStart / padEndrepeat()

Arrays

push / popunshift / shiftmap()filter()reduce()find() / findIndex()includes()some() / every()flat() / flatMap()slice()splice()sort()forEach()Array.from()

Objects

Object literalShorthand propertyComputed propertyOptional chainingObject.keys()Object.values()Object.entries()Object.assign()Spread mergedelete operator

Functions

Function declarationFunction expressionArrow functionDefault parametersRest parametersCallbackIIFE

Conditionals & Loops

if / else if / elseswitchfor loopfor...offor...inwhile / do-whilebreak / continue

Classes

Class definitionInheritanceStatic methodGetter / SetterPrivate fields (ES2022)

Modules (ES6)

Named exportDefault exportNamed importDefault importRename importImport all

Promises

Create.then().catch().finally()Promise.all()Promise.allSettled()Promise.race()

Async / Await

async functionawaittry / catch errorsParallel with await

Fetch API

GET requestPOST requestCheck statusResponse methods

Error Handling

try / catch / finallythrowError types