JavaScript
June 14, 2025 at 12:57 PM
*Useful JavaScript concepts with examples:*
*1️⃣ Variables (let, const, var)*
Used to store data.
```js
let name = "John";
const age = 25;
var city = "Delhi";
```
*2️⃣ Data Types*
Number, String, Boolean, Null, Undefined, Object, Array.
```js
let score = 90; // Number
let isOnline = true; // Boolean
let user = null; // Null
let items = ["pen", "book"]; // Array
```
*3️⃣ Functions*
Reusable blocks of code.
```js
function greet(name) {
return "Hello " + name;
}
greet("Amit"); // Hello Amit
```
*4️⃣ Conditionals (if, else, switch)*
Make decisions.
```js
let marks = 80;
if (marks >= 50) {
console.log("Pass");
} else {
console.log("Fail");
}
```
*5️⃣ Loops (for, while, forEach)*
Repeat actions.
```js
for (let i = 0; i < 5; i++) {
console.log(i);
}
```
*6️⃣ Arrays and Array Methods*
```js
let fruits = ["apple", "banana"];
fruits.push("mango"); // Add item
console.log(fruits.length); // Get length
```
*7️⃣ Objects*
Key-value pairs.
```js
let car = {
brand: "Toyota",
year: 2020
};
console.log(car.brand);
```
*8️⃣ Events (in browser)*
Handle user actions.
```js
document.getElementById("btn").addEventListener("click", () => {
alert("Button clicked!");
});
```
*9️⃣ DOM Manipulation*
```js
document.getElementById("title").innerText = "Updated Text";
```
*🔟 ES6 Features*
- Arrow functions: `const add = (a, b) => a + b;`
- Destructuring: `const { brand } = car;`
- Template literals: ``Hello ${name}``
- Spread/rest: `let newArr = [...fruits]`
*React ❤️ for more*
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