Javascript terms
From DOM manipulation to async superpowers
JavaScript has evolved from a scripting curiosity into a full-stack language powering browsers, servers, and everything in between. This category covers the language core — closures, prototypes, async patterns, the event loop, modern ES2024+ features — as well as runtime behaviour that trips up developers at every experience level. Understanding JavaScript deeply means fewer bugs and more confident code.
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Most referenced — JavaScript
Destructuring & Spread (JS) 2Accidental Object Mutation Bugs 2ES Modules (import/export) 2Client-Side Sanitisation 2JavaScript Bundling — Vite, Webpack, esbuild 2async / await in JavaScript 2CSRF Token Handling in Fetch & Axios 1Custom Events & EventTarget API 1
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ResizeObserver API HTML5
ResizeObserver watches element size changes without polling — more efficient than resize event listeners and works for any element, not just the window.
2mo ago
javascript intermediate
Scheduler API (scheduler.postTask) ES2021
The Scheduler API (scheduler.postTask) lets you prioritise async tasks — user-blocking, user-visible, or background — giving the browser hints to schedule work optimally.
2mo ago
javascript advanced
Streams API — ReadableStream & WritableStream HTML5
The Streams API provides composable, backpressure-aware data pipelines in the browser — processing large responses, files, or media chunk by chunk without buffering everything in memory.
2mo ago
javascript advanced
Top-Level Await in Modules ES2022
ES2022 top-level await lets you use await at the module root without wrapping in async function — blocking module evaluation until the awaited Promise resolves.
2mo ago
javascript intermediate
toSorted / toReversed / with — Immutable Array Methods ES2023
JavaScript ES2023 adds immutable counterparts to mutating array methods: toSorted() returns a sorted copy, toReversed() returns a reversed copy, and with(index, value) returns a copy with one element replaced — none mutate the original array.
2mo ago
javascript beginner
Web Locks API — Coordinating Across Tabs HTML5
The Web Locks API lets JavaScript in the same origin coordinate exclusive or shared access to a named resource across multiple tabs, workers, or iframes — a browser-native mutex.
2mo ago
javascript intermediate
Web Share API HTML5
navigator.share() invokes the native OS share sheet on mobile — letting users share URLs, text, and files via any app installed on their device.
2mo ago
javascript beginner
Accidental Object Mutation Bugs ES2015
Objects and arrays are passed by reference in JS — mutating a function parameter or array element mutates the original, causing subtle cross-component state bugs.
2mo ago
javascript intermediate
Async Error Handling (try/catch + Promise) ES2017
Errors in async functions require try/catch or .catch() — a rejected Promise that's not caught becomes an unhandledRejection that crashes Node or shows a console warning in browsers.
2mo ago
javascript intermediate
Classic Closure-in-Loop Bug (var vs let) ES2015
The most common JavaScript closure bug: using var in a for loop captures the loop variable by reference so all callbacks see the final value — fixed by using let which creates a new binding per iteration.
2mo ago
javascript intermediate
Event Loop Blocking — Long Tasks ES5
JavaScript is single-threaded — synchronous code that runs >50ms blocks the event loop, freezing UI and delaying I/O callbacks. Break long tasks into chunks.
2mo ago
javascript intermediate
Hoisting — var, let, const and function ES5
JavaScript hoists declarations to the top of their scope — var and function declarations are fully hoisted, while let and const are hoisted but remain in the Temporal Dead Zone until their declaration line.
2mo ago
javascript intermediate
Implicit Globals & strict mode ES5
Assigning to an undeclared variable in non-strict mode silently creates a global — use 'use strict' or ES modules to prevent accidental global pollution.
2mo ago
javascript intermediate
Memory Leaks — Closures, Detached DOM ES2015
JavaScript memory leaks occur when references are accidentally retained — common causes: closures holding large objects, detached DOM nodes, forgotten event listeners, and growing Maps/Sets.
2mo ago
javascript advanced
NaN — Detection & Avoiding Pitfalls ES2015
NaN is the only JavaScript value not equal to itself — use Number.isNaN() (not isNaN()) to detect it, as isNaN() coerces its argument first.
2mo ago
javascript beginner
Prototype Chain Errors & hasOwnProperty ES2022
Iterating objects with for...in includes inherited prototype properties — use hasOwnProperty() or Object.keys() to iterate only own properties.
2mo ago
javascript intermediate
ReferenceError — Undefined Variables ES2015
ReferenceError is thrown when accessing a variable that hasn't been declared — unlike undefined which is a declared variable with no value.
2mo ago
javascript beginner
SyntaxError — Parse-Time Failures ES5
SyntaxError means JavaScript couldn't parse your code — the entire script fails to execute. Common causes: missing brackets, invalid JSON, reserved word misuse.
2mo ago
javascript beginner
Temporal Dead Zone (TDZ) ES2015
let and const variables exist in a Temporal Dead Zone from the start of their block until their declaration — accessing them before throws ReferenceError.
2mo ago
javascript intermediate
Type Coercion Gotchas (== vs ===) ES5
JavaScript's == performs type coercion producing surprising results — '0' == false (true), [] == false (true), null == undefined (true) — use === always.
2mo ago
javascript intermediate