Javascript
JS in one word
JS in one word
- JS is a programming language that allows you to implement complex features on web pages.
| 🧠 Concept | 😃 Plain English Explanation |
|---|---|
| Closure | A function that remembers variables from its outer scope |
| Hoisting | JS moves declarations to the top of the file |
| Event Loop | Handles async tasks behind the scenes (like setTimeout) |
| Callback | A function passed into another function to be called later |
| Promise | A value that will be available later (async placeholder) |
| async/await | Cleaner way to write async code instead of chaining .then() |
| Currying | Break a function into smaller, chained functions |
| IIFE | Function that runs immediately after it’s defined |
| Prototype | JS’s way of sharing features across objects (object inheritance) |
| This | Refers to the object currently calling the function |
| Debounce | Delay a function until user stops typing or clicking |
| Throttle | Limit how often a function can run in a time frame |
| Lexical Scope | Inner functions have access to outer function variables |
| Garbage Collection | JS automatically frees up unused memory |
| Shadowing | A variable in a smaller scope overwrites one in a larger scope |
| Callback Hell | Nesting many callbacks leads to messy code |
| Promise Chaining | Using .then() repeatedly to handle multiple async steps |
| Microtask Queue | Where promises get queued (after main code, before rendering) |
| Execution Context | The environment in which JS runs each piece of code |
| Call Stack | A stack where function calls are managed |
| Temporal Dead Zone | Time between variable declaration and initialization with let/const |
| Type Coercion | JS automatically converts types (e.g., "5" + 1 => "51") |
| Falsy Values | Values treated as false (0, "", null, undefined, NaN, false) |
| Truthy Values | Values treated as true ("a", [], 1, ) |
| Short-circuiting | JS skips the rest if result is already known (`true |
| Optional Chaining | ?. safely accesses deep properties without crashing |
| Nullish Coalescing | ?? gives first non-null/undefined value |
| Set & Map | Set = unique values, Map = key-value pairs |
| Memory Leak | When unused data stays in memory and slows the app |
| Event Delegation | One event listener handles many elements efficiently |
| Immutability | Avoid changing existing values — return new ones instead |
| Spread Operator | ... to copy/expand arrays or objects |
| Destructuring | Quickly extract values from arrays/objects |
| Rest Parameters | ...args collects all remaining arguments into one |
| typeof | Tells you the data type of a variable |
| instanceof | Checks if an object belongs to a certain class/type |
| Reference vs Value | Objects/arrays are referenced, primitives are copied |