JavaScript is a language that works with different types of data. Knowing these types is super important to writing good code. If you don’t understand them, your programs might break or behave oddly.
What data types exist in javascript?
A data type tells JavaScript what kind of value you’re working with. It helps the computer know how to handle that value. There are two groups: primitive types and objects. Each one is unique and serves a purpose.
Primitive Data Types in JavaScript
Primitive types are basic. They are simple and can’t be changed once created. These are the foundation of JavaScript.
String
Strings are for storing text. Use quotes to define them.
let greeting = "This is string";
Number
Numbers include whole numbers and decimals. They’re flexible.
let age = 30;
let price = 15.99;
BigInt
BigInt handles massive numbers that normal Number types can’t.
let big = 12345678901234567890n;
Boolean
Booleans are true or false. They help control logic.
let isOnline = false;
Undefined
Undefined means you made a variable, but didn’t assign it a value.
let something;
Null
Null shows that a variable is empty on purpose.
let noValue = null;
Symbol
Symbols are special, unique values. Even if they look the same, they’re different.
let id = Symbol("user");
Objects: The Advanced Types
Objects store related data and functions in one place. They make code more organized and readable.
Basic Object Example
Here’s a simple object:
let user = {
name: "This is user name",
age: 28,
};
namestores"This is user name".agestores28.
Access or update values with dot or bracket notation:
console.log(user.name); // This is user name
user.age = 26; // Updates age to 26
Why Use Objects as Data Types in JavaScript?
Objects help:
- Group related data.
- Represent things like users, products, or settings.
- Combine data and functions.
Adding Functions to Objects
Objects can hold functions too:
let user = {
name: "Some name",
greet() {
return `Hi, I'm ${this.name}!`;
},
};
console.log(user.greet()); // Hi, I'm Some name!
Dynamic Properties
You can add or remove properties anytime:
user.location = "New York"; // Adds a property
delete user.age; // Removes age
console.log(user["location"]); // New York
Special Types of Objects
JavaScript has objects made for specific tasks:
- Array: Stores a list of values in order.
let colors = ["red", "blue", "green"];- Use Case: Managing a list of items such as a to-do list or product catalog.
- Function: Holds reusable code.
function sayHi() { return "Hello!"; }- Use Case: Encapsulating reusable logic, such as a calculation or data transformation.
- Date: For dates and times.
let today = new Date();- Use Case: Scheduling or tracking events, such as showing the current date or calculating deadlines.
- RegExp: Matches patterns in text.
let pattern = /dog/gi;- Use Case: Validating input or searching for patterns in text, such as email validation.
- You can lean more about RegExp from here
- Map: Key-value pairs. Any data type can be a key.
let inventory = new Map(); inventory.set("apples", 10);- Use Case: Managing key-value data, such as storing user preferences or configuration settings.
- Set: Keeps only unique values.
let unique = new Set([1, 2, 2, 3]);- Use Case: Storing unique items, such as tracking visited pages or tags in a blog.
- Typed Arrays: For raw binary data.
let bytes = new Uint8Array([1, 2, 3]);- Use Case: Handling binary data for tasks like image processing or working with Web APIs.
- Promise: Handles async code.
let fetchData = new Promise((resolve) => resolve("Done"));- Use Case: Managing asynchronous operations, such as fetching data from an API.
- Proxy: Customizes how objects behave.
let handler = { get: () => "Intercepted!", }; let proxy = new Proxy({}, handler);- Use Case: Customizing object behavior, such as logging or validating property access.
Meta-Programming in JavaScript
Meta-programming lets you control how your code behaves at runtime. It’s a way to customize or intercept operations on objects. The key tools for meta-programming in JavaScript are Proxy and Reflect.
Proxy
Proxies let you change how objects work. You can intercept actions like getting or setting properties.
Here’s an example:
let target = {};
let handler = {
get: () => "Accessed!",
};
let proxy = new Proxy(target, handler);
console.log(proxy.anything); // Accessed!
target: The original object.handler: Defines custom behavior. In this case, it intercepts property access.proxy: The object that applies the custom behavior.
When to Use Proxies
Proxies are useful for:
- Validation: Checking property values before they’re set.
- Logging: Tracking when properties are accessed.
- Default Values: Returning a fallback value for missing properties.
Example:
let handler = {
get: (obj, prop) => prop in obj ? obj[prop] : "Not Found",
};
let proxy = new Proxy({ name: "Alice" }, handler);
console.log(proxy.name); // Alice
console.log(proxy.age); // Not Found
Proxies give you fine-grained control over objects, making them flexible and powerful.
Reflect
The Reflect object provides methods for working with JavaScript objects. It simplifies operations like setting properties or calling functions.
Example:
let user = { name: "John" };
// Using Reflect to set a property
Reflect.set(user, "age", 30);
console.log(user); // { name: "John", age: 30 }
// Using Reflect to get a property
let name = Reflect.get(user, "name");
console.log(name); // John
// Checking if a property exists
console.log(Reflect.has(user, "age")); // true
When to Use Reflect
Reflect is helpful for:
- Writing clean and consistent object operations.
- Avoiding errors when working with properties or methods.
- Combining with Proxies for advanced custom behavior.
Host Objects
Your environment (browser or Node.js) gives you special objects:
- In Browsers:
window,document,HTMLElement. Learn more from here - In Node.js:
Buffer,process.
Custom Data Types
You can define your own types using classes.
Class Example
class Car {
constructor(make, model) {
this.make = make;
this.model = model;
}
}
let myCar = new Car("Toyota", "Corolla");
Final Thoughts on Data Types
Mastering JavaScript data types makes coding easier. Primitives are simple. Objects are powerful. Use both wisely to build great programs.
You may learn more fom,
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