Welcome! This guide lists over 80 essential JavaScript terms with:
- 📘 Tech Definitions — accurate technical meanings
- 👶 Human Words — simple explanations for beginners
Use this as a quick-reference sheet while learning or coding!
💡 Tip: Use horizontal scroll on smaller screens
| 🏷️ Term | 💻 Tech Definition | 🪄 Human Words |
|---|---|---|
| Arrays | Used to store multiple values in a single variable. They are zero-indexed and can hold mixed data types. | A list of things in one box. You can grab them by number. |
| Async/Await | Way to handle asynchronous operations in JavaScript, built on Promises. | Let the code wait for something to finish before moving on. |
| Arrow Functions | Concise syntax for writing functions, introduced in ES6. | A shorter way to write a recipe (function). |
| ArrayBuffer | A fixed-length binary data buffer used to handle raw binary data. | A block of memory to store binary stuff. |
| Axios | A popular JavaScript library for making HTTP requests. | A tool to get data from the internet easily. |
| Boolean | Represents true or false, used in logical operations and conditional statements. | A light switch: yes (true) or no (false). |
| Browser Object Model (BOM) | Provides APIs to interact with browser features like window management. | Lets you control the browser window itself. |
| Bind (Function Method) | Creates a new function with 'this' bound to a specific object. | Locks a function to always use a certain thing. |
| BigInt | Data type for representing integers larger than Number.MAX_SAFE_INTEGER. | For super huge numbers. |
| Break Statement | Terminates a loop or switch statement. | Stop the loop right now. |
| Callback Functions | Functions passed as arguments to other functions, to be executed later. | A recipe you hand over to use later. |
| Classes | Blueprints for creating objects with methods and properties. | Templates for making similar things. |
| Closures | Functions that remember their lexical scope even when executed outside of it. | A function remembers where it came from. |
| Conditional Statements | Control flow statements for decision-making. | If something is true, do this — otherwise, do that. |
| Const (Declaration) | Declares variables that cannot be reassigned after initialization. | A box you can't change after filling it. |
| Currying | Functional programming technique of taking arguments one at a time. | Breaking a recipe into single steps. |
| DOM (Document Object Model) | Programming interface for HTML and XML documents. | A map of everything on a webpage. |
| Destructuring | Syntax that unpacks values from arrays or objects into variables. | Pulling stuff out of boxes easily. |
| Default Parameters | Allow default values for function parameters. | Use a backup value if nothing is given. |
| Data Types | Categories of values (e.g., number, string, object). | The kind of thing you're working with. |
| Date | Provides methods to work with dates and times. | Tells you the current time or date. |
| Debugging | Process of finding and fixing errors in code. | Finding out why your code is broken. |
| Defer (Script Attribute) | Ensures scripts execute after HTML is parsed. | Wait to run code until the page is ready. |
| Deep Copy | Creates a completely independent copy of an object or array. | A new, separate version of your data. |
| Events | User actions or browser triggers detected by JavaScript. | Something happened, and your code can react. |
| Error Handling | Mechanisms for catching and managing runtime errors. | Catch problems so the program doesn't crash. |
| ECMAScript (ES) | Standard for JavaScript, with various versions introducing features. | The official version of JavaScript. |
| Event Loop | Handles asynchronous operations. | Lets JavaScript wait and resume tasks. |
| Expressions | Code snippets that produce a value. | Something that gives you a result. |
| Encapsulation (OOP) | Hides internal state and allows controlled access. | Keep your data private inside an object. |
| Functions | Reusable blocks of code for specific tasks. | A recipe with steps to follow. |
| For Loop | Iterates over a block of code a fixed number of times. | Repeat this action a set number of times. |
| Fetch API | Modern way to make HTTP requests. | A built-in tool to get data from a server. |
| ForEach | Iterates over elements of an array, executing a function for each. | Do something to each item in a list. |
| Filter | Creates a new array with elements that meet a condition. | Keep only the items that match a rule. |
| Generators | Functions that can be paused and resumed. | A recipe that gives you things one at a time. |
| Getters | Special methods to retrieve object property values. | A function that lets you get data nicely. |
| Global Scope | Variables accessible anywhere in the code. | A box you can reach from anywhere. |
| Garbage Collection | Automatic memory management that reclaims unused memory. | Clean up stuff you don’t need anymore. |
| Higher-Order Functions | Functions that take or return other functions. | Recipes that use or create other recipes. |
| Hoisting | JavaScript moves declarations to the top before execution. | Boxes and recipes go to the top automatically. |
| HTTP Requests | Communicate with servers over the HTTP protocol. | Asking a website/server for data. |
| Iterators | Allow traversal over a collection one element at a time. | Move through a list one step at a time. |
| If-Else Statements | Conditional structures for decision making. | Choose one path or another. |
| IIFE | Functions that execute immediately after being defined. | A function that runs instantly. |
| IndexOf | Finds the first occurrence of a value in a string or array. | Find out where something appears in a list. |
| Inheritance (OOP) | Creates new class based on an existing one. | A child thing copies from a parent. |
| JSON | Lightweight data-interchange format. | A neat way to send data as text. |
| JS Modules | Structure and share code using export/import. | Split your code into smaller, sharable files. |
| JavaScript Objects | Collections of key-value pairs. | A bag of labeled items. |
| Loops | Repeat execution of a block of code. | Do something again and again. |
| Let keyword | Declares variables with block scope. | A flexible box you can change inside limits. |
| Logical Operators | Perform logical operations, often with booleans. | Combine yes/no logic. |
| Math Object | Built-in object for mathematical functions. | Tools for doing math. |
| map() | Creates a new array by applying a function to each element. | Change every item in a list. |
| null | Special value representing intentional absence. | An empty box on purpose. |
| NaN | Special value indicating an invalid number. | “Not a number” — math didn’t work. |
| OOP | Programming with objects and classes. | Code that builds reusable things. |
| Operators | Symbols that perform operations on values/variables. | Math or logic signs like +, ==, &&. |
| Primitive Data Types | Simplest types in JavaScript (string, number, etc.). | Basic building blocks of data. |
| Promises | Object representing the result of an async operation. | A pinky promise: it’ll be done later. |
| Rest Operator (...) | Collects remaining elements into an array or object. | Grab all leftover stuff. |
| Scope | Determines accessibility of variables. | Where your boxes can be seen or used. |
| Strings | Sequences of characters representing text. | Text inside quotes. |
| setTimeout() | Executes a function after a delay. | Wait and then do something. |
| Shallow Copy | Copy where only the first level is duplicated. | A copy that still shares deeper parts. |
| Switch Statement | Control flow for multiple possible cases. | Try different paths until one matches. |
| Ternary Operator | Shorthand for if-else statements. | Quick yes/no choice in one line. |
| Template Literals | Allow embedded expressions in strings. | Fancy strings with variables inside. |
| this Keyword | Refers to the object executing the current function. | "Me" in your current context. |
| Try-Catch | Block to handle exceptions. | Catch problems so your code doesn’t crash. |
| Undefined | Variable declared but not assigned. | A box that exists but is still empty. |
| Unary Operators | Operate on a single operand. | Do something to just one thing. |
| Variables | Containers for storing data values. | Boxes for holding stuff. |
| window Object | Global object representing the browser window. | The browser’s main box. |
| WeakMap | Collection of key-value pairs with object keys. | A map that forgets unused objects. |
| WeakSet | Collection of unique objects held weakly. | A set that forgets things not used. |
🧩 Want to suggest more terms? Feel free to fork and PR!