How AJAX Accesses Web Servers from a Web Page AJAX (Asynchronous JavaScript and XML) allows a web page to communicate with a server without reloading the entire page. The Common Confusion A common question is: If JavaScript runs once and stops, how can AJAX keep talking to a web server? This confusion comes from misunderstanding how JavaScript execution works in the browser. The Key Idea JavaScript does not run only once. It runs again whenever an event happens. AJAX works using: Asynchronous operations Browser-managed networking Callbacks or promises What AJAX Really Is AJAX stands for Asynchronous JavaScript And XML . In practice, ...

Nyquist Theorem for Images The Nyquist theorem applies to images too — not just audio. In images, it is about sampling spatial detail , not time. Simple Explanation The Nyquist theorem states that to accurately represent an image without losing detail, the sampling rate must be at least twice the highest spatial frequency . What is Spatial Frequency? Spatial frequency means how quickly pixel values change across the image. High spatial frequency = sharp edges, fine details Low spatial frequency = smooth areas Meaning in Image Terms If the image has very fine details, you need more pixels to capture them correctly. If you don’t sample enough pixels, aliasing happens (weird patterns, jagged edges, moiré). ...

PSNR (Peak Signal-to-Noise Ratio) PSNR stands for Peak Signal-to-Noise Ratio . It measures how close a processed image or video is to the original, indicating the level of distortion introduced by compression or processing. What it means Signal : the original (reference) image or video Noise : distortion or errors from compression, transmission, or processing PSNR compares the peak signal value to the distortion PSNR is expressed in decibels (dB) . Why it matters Higher PSNR → less distortion → better visual quality Lower PSNR → more visible artifacts and degradation PSNR is widely used in: Image compression (JPEG, PNG, WebP) Video compression (H.264, H.265, AV1) Image and video quality eva...

OSNR (Optical Signal-to-Noise Ratio) OSNR stands for Optical Signal-to-Noise Ratio . In simple terms, it tells you how clean an optical signal is compared to the noise around it — like comparing music volume to background static. What it means Signal : the actual light carrying your data Noise : unwanted light (amplifier noise, spontaneous emission, etc.) OSNR measures the ratio between them OSNR is usually expressed in decibels (dB) . Why it matters OSNR is critical in fiber-optic communications: Higher OSNR → cleaner signal → lower bit-error rate Lower OSNR → more errors, distortion, or link failure It is especially important in: DWDM systems Optical amplifiers (e.g., EDFAs) ...

BMR Calculator Personal Details Gender Male Female Age (years) Height (cm) Weight (kg) Activity Level Sedentary (little or no exercise) Lightly active (1–3 days/week) Moderately active (3–5 days/week) Very active (6–7 days/week) Super active (physical job) Calculate How it Calculates? Results How This Calculator Works 1. BMR (Basal Metabolic Rate) BMR is the number of calories your body needs to perform basic functions like breathing and digestion while at rest. Male : BMR = 10 × Weight + 6.25 × Height − 5 × Age + 5 Female : BMR = 10 × Weight + 6.25 × Height − 5 × Age − 161 2. Daily Calorie Needs (TDEE) Total Daily Energy Expenditure (TDEE)...

Understanding Async Code (Without the Confusion) Many beginners hear async and think it means doing many things at the same time. That sounds reasonable — but it’s not what async really means. Let’s fix that. The Core Idea Async does NOT mean parallel. Async means deferred. Think of async code as a to-do list . The program finishes what it is doing now, postpones slow tasks, and comes back to them when they are ready. One Brain, One Task Both JavaScript and Python behave like a single person with one brain: They run code top to bottom They do one thing at a time They don’t multitask by default Async allows them to avoid waiting and freezing while slow tasks complete. Real-Life Analogy Imagine cooking: You pu...

Inheritance in JavaScript Inheritance in JavaScript allows one class to acquire the properties and methods of another class. This helps in reusing code, reducing duplication, and organizing programs in a clear and logical way. The extends keyword is used to create a child class that inherits from a parent class. The super() method is used inside the child class to call the constructor of the parent class. Example: Car and Model Classes In this example, the Car class is the parent class, and the Model class is the child class that inherits from it. class Car { constructor(brand) { this.carname = brand; } present() { return 'I have a ' + this.carname; } } class Model extends Car { constructor(brand, mod) { super(brand); // Call the parent constructor this.model = mod; } show() { return th...

FD / RD / PPF Calculator Fixed Deposit (FD) Principal Amount (₹) Interest Rate (%) Time Period (Years) Calculate FD Recurring Deposit (RD) Monthly Investment (₹) Interest Rate (%) Time Period (Years) Calculate RD Public Provident Fund (PPF) Yearly Investment (₹) Interest Rate (%) Investment Duration (Years) Calculate PPF Rules for Calculation FD uses annual compound interest RD uses monthly compounding PPF compounds yearly with government-declared rate PPF has a minimum lock-in of 15 years ...