🌐 What is the DOM? The DOM is a programming interface for web documents. It represents the HTML or XML document as a tree structure. Each element (like <div>, <p>, <h1>, etc.) becomes a node in this tree. Example: <html> <body> <h1>Hello</h1> <p>World</p> </body> </html> <html> <body> <h1>Hello</h1> <p>World</p> </body> </html> DOM Tree Representation:…
1. Local Storage Purpose: Stores data in the browser that persists even after the browser is closed. Lifespan: Permanent until explicitly cleared by the user or program. Storage Limit: Usually 5-10 MB per domain. Accessibility: Only accessible on the client-side (browser), not sent with HTTP requests. Example: // Store data localStorage.setItem('username', 'Alice'); // Retrieve…
1. The Basics of try/catch try/catch lets you handle errors gracefully instead of letting your program crash. Syntax: try { // Code that might throw an error } catch (error) { // Code to handle the error } finally { // Optional: code that runs regardless of error } try { // Code that…
1. What is fetch()? fetch() is a modern JavaScript function that allows you to make network requests (like GET, POST, etc.) to APIs. It returns a Promise, which resolves to the Response object. 2. Basic fetch() Example Suppose we want to get some data from a public API: JSONPlaceholder (fake API for testing). //…
1. Filters in MongoDB Filters are used in queries to select documents that match certain conditions. You generally use find() for this. Example: Suppose we have a collection employees: [ { "_id": 1, "name": "Alice", "age": 30, "department": "HR", "salary": 5000 }, { "_id": 2, "name": "Bob", "age": 25, "department": "IT", "salary": 6000 },…
Here’s a clear breakdown of the differences between SQL and NoSQL databases: FeatureSQL (Relational)NoSQL (Non-Relational)Data ModelStructured, table-based with rows and columnsFlexible, can be document, key-value, column-family, or graph-basedSchemaFixed schema; must define tables and column types beforehandDynamic or flexible schema; fields can vary across documentsQuery LanguageUses SQL (Structured Query Language) for complex queriesUses varied query…
The N+1 problem is a common performance issue in programming, especially when dealing with databases and object-relational mapping (ORM) frameworks. It occurs when an application makes one query to fetch a list of items (the “1”) and then makes an additional query for each item in the list (the “N”), resulting in many more…
1. Partitioning Definition:Partitioning is the process of dividing a single database table into smaller, more manageable pieces, called partitions, while still keeping them within the same database. Each partition can be stored separately, often based on some key (like date, region, or ID). Purpose: Improves query performance. Makes management easier (backups, archiving). Can reduce…
In SQL (Structured Query Language), Security and Permissions are mechanisms that control who can access the database and what actions they are allowed to perform.This ensures that sensitive data is protected and only authorized users can read, insert, update, or delete data. 1. Authentication Determines who the user is (login system). Example: In SQL…
🔹 What is a Transaction? A transaction is a sequence of one or more SQL statements executed as a single unit of work.It ensures the ACID properties: Atomicity → all or nothing Consistency → maintains data integrity Isolation → transactions don’t interfere with each other Durability → once committed, changes are permanent 🔹 Transaction…