标签：#JavaScript

Ich habe einen echten Speedtest in Vanilla JS gebaut (mit Cloudflare API) Kein npm install. Kein React. Kein 200-MB-node_modules-Ordner. Nur HTML, CSS und ~250 Zeilen JavaScript, die deine echte Internetgeschwindigkeit messen. 👉 Live-Demo: dsl.nevik.de/speedtest Warum noch ein Speedtest? Es gibt Speedtest.net, FAST.com und dutzende andere. Warum also selbst bauen? Drei Gründe: Transparenz: Ich wollte genau verstehen, was gemessen wird – und was nicht. Größe: Die meisten kommerziellen Speedtests laden mehrere MB an Tracking-Scripts. Meiner ist eine einzige HTML-Datei mit eingebettetem JS. Kontrolle: Ich kann das Ergebnis direkt gegen den gebuchten Tarif des Nutzers bewerten und eine fundierte Empfehlung geben. Das Ergebnis ist ein Speedtest, der in unter 50 KB ausgeliefert wird, auf jedem Gerät läuft und echte Messwerte liefert – keine Schätzwerte. Die Architektur: Drei Phasen, drei Messungen Ein guter Speedtest misst drei Dinge: Ping (Latenz): Wie schnell kommt ein Datenpaket hin und zurück? Download: Wie schnell kommen Daten bei dir an? Upload: Wie schnell kommen Daten von dir raus? Für alle drei nutze ich die öffentliche Cloudflare-Speedtest-API , die unter speed.cloudflare.com läuft. Cloudflare betreibt eines der größten Edge-Netzwerke der Welt, hat Server in praktisch jedem Land und – ganz wichtig – erlaubt CORS für diese Endpunkte, sodass wir direkt aus dem Browser heraus messen können. Die zwei Endpunkte, die alles tragen: const CF_DOWN = ' https://speed.cloudflare.com/__down?bytes= ' ; const CF_UP = ' https://speed.cloudflare.com/__up ' ; __down?bytes=N liefert exakt N Bytes zurück. __up nimmt einen POST-Body beliebiger Größe entgegen. Das war's. Kein API-Key, keine Rate-Limits, die für unsere Zwecke relevant wären, keine Kosten. Phase 1: Ping messen (ohne WebSocket) Klassische Speedtests nutzen für den Ping oft WebSockets oder RTCPeerConnection -Tricks. Das ist komplex und fehleranfällig. Mein Ansatz: Wir laden einfach einen winzigen Datenblock (1 KB) fünfma

I just wanted to open a CSV file quickly. Instead, I got: Slow spreadsheet apps Online tools that upload my data Way too much friction So I defined a simple goal: Fast and frictionless Fully local (no uploads) Spreadsheet-like experience That’s what I built. What you can do with it Open CSV files instantly (drag & drop, no setup) Search and filter large datasets in seconds Edit data like a spreadsheet Export exactly what you see Why this matters Everything happens locally in your browser: Your data never leaves your device No account required No tracking, no storage Built with client-side JavaScript — no backend involved. Just open, edit, and export. How it works Built with client-side JavaScript — no backend involved. Spreadsheet-Like Editing Click a cell to select it, then press Enter or double-click to start editing. Press Enter again to save the value and move to the cell below. Use Option + Enter on macOS or Alt + Enter on Windows to insert a line break. You can also drag the small fill handle to copy a value across multiple cells. Export the Current View The exported CSV reflects the current table state, including: Search results Sorting order Visible columns Saved cell edits Try it yourself Open a CSV file, edit a few cells, and export it — all without uploading anything. 👉 https://csv-open.github.io/ No signup. No upload. Just works. Handles CSV files up to 25MB Supports multiple languages

What happens when 5 parallel API calls hit for an expired JWT at the exact same millisecond. Imagine this: You’ve built a sleek, high-performance React dashboard. The UI is sharp, dark mode is gleaming, components are modularized, and React Query is executing parallel data fetches like a grand symphony. You brew a cup of coffee, open the app after lunch, hit refresh, and… BAM! You are immediately booted back to the Login screen. No warnings, no friendly error toasts—just a cold, ruthless redirect. You check your JWT expiration timer. The access token died 5 seconds ago, but your refresh token is valid for another 14 days. So why on earth did your app decide to kick you out like an uninvited party crasher? Welcome to the chaotic nightmare of Token Refresh Race Conditions in Axios Interceptors . In this article, we’ll walk through how parallel React queries can accidentally DDOS your own backend, why standard interceptor tutorials fail in production, how we built a promise-queue lock mechanism to solve it, and the subtle "gotcha" lurking in simple error detail checks that almost broke everything anyway. 1. The Problem: The Dashboard Stampede When a user logs into our app and opens the main dashboard, React Query triggers a stampede of concurrent API requests: GET /api/teams/users/ (Fetch team members) GET /api/teams/addresses/ (Fetch locations) GET /api/auth/profile/ (Fetch user profile) GET /api/auth/activity/recent/ (Fetch activity log) GET /api/notifications/ (Fetch unread alerts) Under normal circumstances, all five requests ride happily on the same valid Bearer <access_token> HTTP header. React App ---------------------------------------------> Django Backend GET /users/ [Bearer valid] ---> 200 OK GET /locations/ [Bearer valid] ---> 200 OK GET /profile/ [Bearer valid] ---> 200 OK The Ticking Time Bomb Fast forward 15 minutes. The short-lived access token expires. The user clicks on the "Analytics" tab. All 5 queries trigger at the exact same millisecond ( T = 0ms

Jotai v2.20.0 has been released, focusing on improved performance for high-throughput scenarios. Key changes involve adjustments to internal building blocks and addressing previous performance regressions. While the API for everyday use remains unchanged, library authors should note some deprecations as the groundwork for Jotai v3 begins. By Daniel Curtis

When building a website, choosing a button design can take more time than expected. You may want something simple, soft, colorful, dark, outlined, or slightly unusual—but comparing many styles usually means repeatedly editing CSS and refreshing the page. To make that process easier, I created a browser-based button showcase. Try It Online You can use it directly from the following page: https://uni928.github.io/Uni928PublicHTMLs/index78.html There is nothing to install. Open the page, browse the available designs, and choose a button you like. Many Button Styles in One Place The page includes a wide range of button designs, including: Light and subtle buttons Solid-color buttons Dark buttons Gradient buttons Outline buttons Rounded and pill-shaped buttons Buttons with icons More experimental designs The buttons are displayed as actual interactive elements, so you can compare their hover, focus, and pressed states directly in the browser. Click a Button to Copy It The main feature of this tool is its copy workflow. Clicking a button copies a minimal HTML example for that design. This makes it easier to take only the button you need instead of copying the entire showcase page. The generated example includes the necessary HTML and CSS, so it can be pasted into a new file and tested immediately. Copy Features for Faster Comparison The site also includes additional copy-related features to make browsing a large number of designs more convenient. You can: Copy a button directly by clicking it Review the generated code Copy frequently used button types from the quick-copy panel Receive visual feedback after a successful copy Use copied examples as standalone HTML files This is especially useful when you want to compare several designs before deciding which one to use in a project. Useful for Prototypes and Small Projects This tool is intended for situations where you need a usable button quickly, such as: Creating a prototype Building a small static website Testing a landi

The Challenge Rendering a complex 153-concept-node, 1,200-edge mythic relationship topology for mobile devices without triggering main-thread layout thrashing or heavy client-side JavaScript execution. The Technical Approach Build-Time D3 Force Layout Computation : Pre-computing node coordinates and physics simulation during the Astro static build step. Zero-Runtime SVG Pre-rendering : Outputting the rendered topology as inline SVG with CSS design tokens, preserving 60 FPS scrolling on mobile. Canonical Lore Data Architecture : Structuring 153 canonical concept nodes across Tang Dynasty exorcistic texts ( Nuo rituals) and Black Myth: Zhong Kui motifs. Check out the live interactive relationship map: Black Myth Lore & Concept Map Official website: blackmyth.game

Serious engineering teams pay a quiet tax: dependency alerts nobody trusts, full test suites on one-line PRs, and CI YAML that only fails after a push. I built three small open-source CLIs that attack those loops: Tool Install Job vulntriage npm i -g vulntriage Which CVEs matter impactest npm i -g impactest Which tests to run gha-step npm i -g gha-step Run CI shell steps now npx vulntriage . --group --fail-on fix_now npx impactest -f vitest -q | xargs -r npx vitest run npx gha-step run test --dry-run All Apache-2.0. No SaaS. Designed to earn a place in CI by being boringly explainable. Canonical: https://sybilgambleyyu.github.io/posts/tool-family.html

1. Introduction: What is TanStack Query? TanStack Query (formerly React Query) is a framework-agnostic state management library designed specifically to manage Server State —handling data fetching, caching, background updating, and cache invalidation. 2. Server State vs. Client State & The Memory Reality Client State: Owned and controlled entirely by the browser (e.g., isModalOpen , selected UI theme). Server State: Owned by the remote backend database (e.g., user profiles, posts, cart items). The browser only holds a read-only temporary snapshot . Where is data physically stored? Physical Location: By default, cached data lives strictly in the browser tab's JavaScript RAM (In-Memory) . Backend ("The Server"): Refers to your remote API/database (regardless of whether it runs on Kubernetes, Docker containers, serverless functions, or bare metal). Optional Persistence: You can opt to sync this RAM cache to localStorage , sessionStorage , or IndexedDB using TanStack Query Persisters. import React , { useState } from ' react ' ; import { QueryClient , QueryClientProvider , useQuery , useMutation , useQueryClient , } from ' @tanstack/react-query ' ; // 1. Initialize QueryClient (manages the RAM cache) const queryClient = new QueryClient ({ defaultOptions : { queries : { staleTime : 10000 , // Data stays fresh in RAM for 10 seconds }, }, }); // Mock API functions async function fetchPost ( postId ) { const res = await fetch ( `[https://jsonplaceholder.typicode.com/posts/$](https://jsonplaceholder.typicode.com/posts/$){postId}` ); if ( ! res . ok ) throw new Error ( ' Network error ' ); return res . json (); } async function createPost ( newPost ) { const res = await fetch ( ' [https://jsonplaceholder.typicode.com/posts](https://jsonplaceholder.typicode.com/posts) ' , { method : ' POST ' , headers : { ' Content-Type ' : ' application/json ' }, body : JSON . stringify ( newPost ), }); return res . json (); } // 2. Query Component (Fetching & Reading Data) function PostViewe

Every developer has had this moment. You need a date picker, so you start searching. You find one that's perfect... until you realize it requires React. Or Vue. Or jQuery. Or an entire date library just to select a few dates. After trying several solutions, I kept asking myself: Why is such a common UI component often more complicated than it needs to be? So I decided to build my own. Meet RollDate . The Goal I didn't want to create "another date picker." I wanted to build something that I would actually enjoy using in my own projects. The goals were simple: Infinite scroll Zero framework dependencies Simple API Modern UI Mobile-friendly scrolling TypeScript support Easy customization Good documentation Why Scrolling? Most date pickers rely on clicking tiny arrows or dropdowns. On mobile devices, this often feels awkward. I wanted something closer to native mobile pickers, where changing the month or year is just a smooth scroll. That became one of RollDate's core ideas. More Than Just Picking a Date While building the component, I realized different projects need different selection modes. So instead of maintaining separate components, RollDate supports: Single date selection Date range selection Multiple date selection The API stays the same regardless of the mode. new RollDate ( " #date " , { selectType : " range " }); Optional Time Picker Many date pickers force you to install another plugin if you need time selection. I wanted it built in. RollDate supports: 24-hour mode 12-hour AM/PM mode Configurable minute steps Enable it with one option. new RollDate ( " #date " , { enableTime : true }); Dependency-Free One of the main design goals was keeping the library independent. No React. No Vue. No jQuery. No Moment.js. No Day.js. Just plain JavaScript. That means it works almost anywhere: Vanilla JavaScript React Vue Angular Svelte Astro ...or any framework capable of using DOM components. A Better Developer Experience I care a lot about developer experience. That's

If you have ever tried building a website change detection system or visual testing tool, you’ve likely stumbled into the "False Positive Trap." You configure a cron job to monitor a target URL, take snapshots every 15 minutes, and compare them. But within hours, your inbox is flooded with alerts for: Tailwind CSS dynamic hash class mutations (e.g. class="bg-blue-500_a3f9" turning into class="bg-blue-500_b81c" after a deployment) Lazy-loaded images rendering at offset offsets Anti-bot verification scripts altering invisible DOM nodes Hydration mismatches in React/Vue single-page applications At PageWatch.tech , solving these exact edge cases was the primary focus of our engineering roadmap. In this article, I’ll share the 3 core algorithmic fixes we implemented to achieve reliable, noise-free website change monitoring. 🛑 Problem 1: Structural Hash Instability in Modern Frameworks Modern frontend frameworks like Next.js, Nuxt, and Remix insert dynamic build IDs, hydration keys, and inline CSS chunk hashes into the HTML structure. For example, a innocent paragraph tag might look like this today: <p class= "text-gray-700 css-1a2b3c" data-reactroot= "" > Product Price: $99 </p> And like this tomorrow after a routine production deployment: <p class= "text-gray-700 css-9x8y7z" data-reactroot= "" > Product Price: $99 </p> A standard raw string comparison flags this as a critical change even though zero user-facing content changed . The Solution: Attribute Normalization & CSS Class Sanitization Before computing DOM structural hashes, we run a normalize pass that strips generated hashes and framework-specific attributes: import * as htmlparser2 from " htmlparser2 " ; /** * Normalizes dynamic framework attributes and hashed CSS classes * before running DOM diff calculations. */ export function normalizeDOMNode ( node : any ): void { if ( node . attribs ) { // 1. Remove hydration and framework metadata const volatileAttrs = [ " data-reactroot " , " data-reactid " , " data-hydr

You have read five blog posts about monads. Each one started with category theory, mentioned burritos, and left you more confused than before. Let's skip all of that. Here is the short version: a monad is a container that supports three operations. You already use two monads every day in TypeScript — Promise and Array . Once you see the pattern, every monad in @oofp/core will feel familiar. The Three Operations Every monad has three things: of(a) — Put a value into the container. map(f) — Transform the value inside, keep the container shape. chain(f) — Transform the value into a new container, then flatten. That's it. If a type supports these three operations and follows a few simple laws, it's a monad. Let's see this with types you already know. Promise — a monad you use daily // of — wrap a value const p = Promise . resolve ( 42 ); // map — transform the inside (then with a plain return) const doubled = p . then (( x ) => x * 2 ); // Promise<number> // chain — transform into a new Promise (then with an async return) const fetched = p . then (( id ) => fetch ( `/api/users/ ${ id } ` )); // Promise<Response> Promise.resolve is of . .then acts as both map and chain — JavaScript conflates them. When your callback returns a plain value, it's map . When it returns a Promise , it's chain . The runtime flattens the nested Promise<Promise<T>> into Promise<T> automatically. Array — another monad hiding in plain sight // of — wrap a value const arr = [ 42 ]; // map — transform each element const doubled = arr . map (( x ) => x * 2 ); // [84] // chain — transform each element into an array, then flatten const expanded = arr . flatMap (( x ) => [ x , x * 10 ]); // [42, 420] Array.of (or just [value] ) is of . .map is map . .flatMap is chain . Same pattern, different container. The insight is: chain is map followed by flatten . That's why it's also called flatMap or bind . You apply a function that returns a new container, then flatten the nested result. Maybe: Eliminating null

I have been quiet lately I know - but don't worry I haven't forgotten you all and how much you like...

GitHub热门项目 | Prompt as Code | GPT-Image2 工业级提示词引擎与模板库，470+ 个案例逆向工程，20+ 套工业级模板，并提炼出Skills，持续更新中 | Stars: 8,643 | 49 stars today | 语言: JavaScript

You've probably seen this: Kubernetes probes are green, /health returns 200, CPU isn't on fire - and users are timing out. Process is up. Just not doing anything useful. Classic event loop freeze. Something sync and expensive (or a dumb busy loop) grabs the thread, and suddenly timers, HTTP, DB callbacks - all of it waits. Including your health endpoint, because that also needs the loop. monitorEventLoopDelay() is fine for dashboards. It won't yell at you while the process is stuck, and it definitely won't write a log line from outside the frozen loop. That's the part that annoyed me enough to build this. I made @js-ak/watchdog - tiny N-API addon. The monitor runs in C++ on its own thread and writes JSON lines to stderr/file even while the JS event loop is stuck. Your freeze / recovered handlers only run after the loop unblocks. Optional RSS/CPU, optional stack sample. npm install @js-ak/watchdog const watchdog = require("@js-ak/watchdog"); watchdog.on("freeze", (e) => console.log(e.event, e.duration_ms)); watchdog.on("recovered", (e) => console.log("back after", e.duration_ms, "ms")); watchdog.start({ freezeThresholdMs: 1000, logTarget: "stderr", // or "file" | "both" source: "payments-api", }); Real freezes usually aren't while (true) . More like giant JSON.parse, a cursed regex, sync crypto/compress, or some dependency doing sync I/O on a hot path. Stuff you only notice after people complain. Prebuilds for the usual platforms (Node 22+). MIT. Repo: https://github.com/JS-AK/watchdog Curious how other people catch loop stalls in prod - and what you'd actually want in the freeze payload. Roast the API if it's wrong.

Watermarking a PDF — adding semi-transparent text over pages — sounds like something only desktop software handles. But with pdf-lib and a bit of canvas math, you can build a fully browser-based watermark tool. This post walks through the implementation details, including text rendering, rotation, and multi-page support. Why client-side? Traditional watermark tools upload your file, process it on a server, and send the result back. For documents that might be confidential or contain sensitive information, this introduces an unnecessary privacy risk. A browser-based approach: Processes everything locally Keeps files on the user's device Works offline after loading Avoids server-side bandwidth costs The stack Vue 3 + Composition API pdf-lib for PDF manipulation and watermarks PDF.js ( pdfjs-dist ) for preview rendering Vite for bundling Adding a text watermark pdf-lib provides a built-in PDFDocument.embedFont() method for custom fonts and page.drawText() for placing text. Here's how to add a rotated, semi-transparent watermark across all pages: < script setup lang= "ts" > import { ref } from ' vue ' import { PDFDocument , rgb , StandardFonts } from ' pdf-lib ' const file = ref < File | null > ( null ) const watermarkText = ref ( ' DRAFT ' ) const opacity = ref ( 0.3 ) const fontSize = ref ( 72 ) const rotationDeg = ref ( - 45 ) const applying = ref ( false ) async function handleFileUpload ( selected : File ) { file . value = selected } async function applyWatermark () { if ( ! file . value ) return applying . value = true try { const arrayBuffer = await file . value . arrayBuffer () const pdfDoc = await PDFDocument . load ( arrayBuffer ) // Embed the Helvetica font — required for correct rendering const helveticaFont = await pdfDoc . embedFont ( StandardFonts . HelveticaBold ) const pages = pdfDoc . getPages () pages . forEach (( page ) => { const { width , height } = page . getSize () page . drawText ( watermarkText . value , { x : ( width - helveticaFont . widthOfT

If you've been developing with React Native or Expo for a while, chances are you've had a project that suddenly refuses to build for what seems like no reason. Maybe you installed a new package. Maybe you upgraded Expo. Maybe you only changed a single dependency. You confidently run your Android build, expecting it to compile like always... Instead, Gradle greets you with something like this: Execution failed for task ':app:checkDebugDuplicateClasses'. Duplicate class androidx.lifecycle.ViewModelLazy found in modules lifecycle-viewmodel-2.8.2.aar and lifecycle-viewmodel-ktx-2.6.1.aar Duplicate class com.google.android.gms.internal.measurement.zzab found in modules play-services-measurement-base-22.0.0.aar and play-services-measurement-impl-21.6.2.aar Duplicate class ... At first glance, the error looks straightforward: there are duplicate classes . Easy enough, right? Not exactly. In reality, this is one of those Android build errors that can send you down a rabbit hole of Gradle files, dependency trees and Stack Overflow threads, only to realize the real cause was something completely different. Let's break down what's actually happening and, more importantly, how to fix it. Why this error happens Every Android library included in your project contains compiled Java or Kotlin classes. When Gradle builds your application, it combines all of those libraries into a single APK or AAB. If two different dependencies contain the exact same class, Gradle doesn't know which version should be packaged. Instead of guessing, it stops the build with a Duplicate class error. The difficult part is that the dependency causing the conflict usually isn't the one shown in the error. Very often, it's another package pulling in an older or incompatible version behind the scenes. The most common causes After seeing this error many times, these are usually the culprits. 1. Two libraries depend on different versions of the same package This is by far the most common scenario. For example:

Hi, my name is Dan, I'm a frontend engineer and open-source maintainer. I've spent the last couple of years building Nano Kit — a lightweight, modular state management ecosystem for modern web apps: signals-based stores , a router , data fetching , i18n , and SSR support , all built on the same tiny reactive core. It recently hit 1.0 , and in this post I want to give you four honest reasons to try it. 1. It's fast At the heart of Nano Kit is a push-pull reactivity system based on the algorithm from alien-signals — one of the fastest signal implementations in the JavaScript ecosystem. I didn't use alien-signals directly, though. Nano Kit needed things it doesn't provide, so I built a dedicated fork called Agera : Signal lifecycles — you can listen to signal activation and deactivation, which powers Nano Kit's mountable stores (run setup logic on first listener, clean up on last). Real tree-shaking — Agera is designed so that only the code you use ends up in your bundle; alien-signals is not well tree-shakable. The result keeps almost all of alien-signals' raw speed. Here is how @nano_kit/store compares to other popular state management libraries in a reactivity benchmark : Library Latency avg (ns) Throughput avg (ops/s) alien-signals 294.00 ± 2.24% 3,559,763 @nano_kit/store 303.55 ± 0.75% 3,365,816 svelte/store 428.58 ± 0.61% 2,479,118 rxjs 454.74 ± 0.07% 2,250,397 nanostores 1,373.2 ± 5.96% 952,399 mobx 3,474.7 ± 1.86% 306,094 valtio 5,041.3 ± 11.46% 254,109 jotai 9,454.6 ± 16.45% 157,853 effector 24,885 ± 11.78% 62,744 @reatom/core 59,430 ± 15.61% 22,741 Benchmark was run on AMD Ryzen 5 PRO 3400G with Node.js v24.14.1 That's ~3.5× faster than nanostores and an order of magnitude faster than most atomic state managers — while shipping lifecycles and mountable stores on top. 2. It's small Nano Kit exists largely because of Nano Stores . I love its philosophy: atomic stores, mountable resources, logic moved out of components, and an obsessive focus on bundle size. Nan

A background worker sits quietly for weeks, chewing through a job queue without incident, and then one Tuesday afternoon it disappears mid-batch, taking forty in-flight jobs down with it. No stack trace pointing at the offending line, no alert until a customer notices their export never finished. Nine times out of ten, the culprit is one of the most under-discussed failure modes in server-side JavaScript: unhandled promise rejections. They are easy to introduce, easy to miss in code review, and in modern Node.js they no longer just print a warning — they can end your process outright. This post walks through what unhandled promise rejections actually are at the engine level, why they are far more dangerous in long-running Node.js services than in typical web requests, how Node's default behavior around them has shifted over the years, and the concrete patterns you can use to stop them from quietly killing your jobs. What an Unhandled Promise Rejection Actually Is At the JavaScript engine level, a promise is a state machine with three possible states: pending, fulfilled, or rejected. When an async operation fails — a network call times out, a database query throws, a JSON parse blows up — the promise representing that operation transitions to the rejected state and carries a reason, usually an Error object. That's all a rejection is: a value flowing down the promise's error channel instead of its success channel. The engine only considers a rejection "handled" if, by the time it does its bookkeeping (which happens on a microtask checkpoint, not synchronously), there is a .catch() handler, a second argument to .then() , or a surrounding try/catch around an await somewhere in that promise's chain. If none of those exist anywhere in the chain, the rejection is classified as unhandled. This is the precise, narrow definition of unhandled promise rejections: a promise that reaches the rejected state with zero handlers attached anywhere along its chain of consumers. It's wo

I'll guide you through Python fundamentals by comparing concepts with JavaScript. Let's start! 1. Hello World & Basic Syntax JavaScript console . log ( " Hello World " ); let x = 5 ; Python print ( " Hello World " ) x = 5 # No semicolon, no let/const Key Differences: No semicolons in Python Indentation matters (replaces curly braces) Comments use # instead of // 2. Variables & Data Types JavaScript let name = " Alice " ; // string let age = 30 ; // number let isStudent = true ; // boolean let scores = [ 95 , 87 , 91 ]; // array let person = { // object name : " Bob " , age : 25 }; let nothing = null ; let notDefined = undefined ; Python name = " Alice " # str age = 30 # int (or float for decimals) is_student = True # bool (capital T/F) scores = [ 95 , 87 , 91 ] # list (mutable) person = { # dict (dictionary) " name " : " Bob " , " age " : 25 } nothing = None # Python's null/undefined Key Differences: Python uses snake_case (not camelCase) True / False capitalized None instead of null / undefined Lists ≈ Arrays, Dicts ≈ Objects 3. Control Flow JavaScript // If-else if ( age >= 18 ) { console . log ( " Adult " ); } else if ( age >= 13 ) { console . log ( " Teen " ); } else { console . log ( " Child " ); } // For loop for ( let i = 0 ; i < 5 ; i ++ ) { console . log ( i ); } // While loop let count = 0 ; while ( count < 5 ) { console . log ( count ); count ++ ; } Python # If-else (indentation instead of braces) if age >= 18 : print ( " Adult " ) elif age >= 13 : # NOT else if print ( " Teen " ) else : print ( " Child " ) # For loop (more like for...of in JS) for i in range ( 5 ): # range(5) = [0, 1, 2, 3, 4] print ( i ) # Iterate over list (like for...of) for score in scores : print ( score ) # While loop count = 0 while count < 5 : print ( count ) count += 1 # No ++ operator in Python 4. Functions JavaScript // Function declaration function add ( a , b ) { return a + b ; } // Arrow function const multiply = ( a , b ) => a * b ; // Default parameters function greet ( n

Nowadays, web frameworks come with ✨ magic ✨. Some more than others, but all of them have some. The...