tryjs.app

Runnable JavaScript and TypeScript examples

Start from working JavaScript, async, and TypeScript examples, then open them in the TryJS playground to edit, run, share, or extend.

JS Fundamentals

Map, Filter, Reduce

Transform, filter, and aggregate arrays

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Destructuring

Object and array destructuring patterns

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Spread & Rest

Spread operator and rest parameters

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Closures

Functions that capture their scope

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Map & Set

Built-in collection types

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Optional Chaining

Safely access nested properties with ?.

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Nullish Coalescing

Default values with ?? — safer than ||

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Debounce vs Throttle

Rate-limiting functions — two common strategies

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Deep Clone

structuredClone vs JSON vs manual

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The 'this' Keyword

How 'this' is determined at call time

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Hoisting

var, let, const, and function declarations

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for...of vs for...in

Choosing the right iteration syntax

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Memoization

Cache function results for speed

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Async Patterns

Promise.all

Run async operations in parallel

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Async/Await Error Handling

Try/catch with async functions

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Promise.race & allSettled

Advanced Promise combinators

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Event Loop Demo

Microtasks vs macrotasks — execution order explained

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Async Iterators

for await...of and async generators

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TypeScript Essentials

Generics

Type-safe generic functions and types

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Type Guards

Narrow types with custom guards

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Utility Types

Built-in mapped and conditional types

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Discriminated Unions

Exhaustive pattern matching

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