JavaScript Loops Kya Hote Hain?

Introduction to Loops

JavaScript me loops ka use kisi bhi task ko repeat karne ke liye kiya jata hai. Agar hume ek hi code ko multiple times execute karna ho, to loops ka use bahut helpful hota hai. Yeh code ko concise aur maintainable banata hai. JavaScript me different types ke loops hote hain jo alag-alag situations ke liye use kiye jate hain.

1. The for Loop

for loop ek control flow statement hai jo ek block of code ko ek fixed number of times execute karne ke liye use hota hai. Yeh loop initialization, condition, aur increment/decrement ke sath kaam karta hai.

for (let i = 1; i <= 5; i++) {
  console.log("Number: " + i);
}

2. The while Loop

while loop ek condition ke true hone tak continuously execute hota rehta hai. Yeh tab useful hota hai jab hume pehle se nahi pata hota ki kitni baar loop chalana hai.

let i = 1;
while (i <= 5) {
  console.log("Count: " + i);
  i++;
}

3. The do-while Loop

Yeh loop while loop jaisa hi hai, lekin isme code block kam se kam ek baar zaroor execute hota hai, chahe condition false hi kyu na ho.

let i = 1;
do {
  console.log("Value: " + i);
  i++;
} while (i <= 5);

4. The for...in Loop

for...in loop ka use object ki properties ko iterate karne ke liye hota hai. Yeh har iteration me property ka naam (key) return karta hai.

const student = { name: "Rahul", age: 20, city: "Delhi" };

for (let key in student) {
  console.log(key + ": " + student[key]);
}
// Output:
// name: Rahul
// age: 20
// city: Delhi

5. The for...of Loop

for...of loop (ES6 me introduce hua) iterable objects (jaise Arrays, Strings, Maps) ki values ko iterate karne ke liye use hota hai.

const numbers = [10, 20, 30, 40];

for (let num of numbers) {
  console.log(num);
}
// Output: 10, 20, 30, 40

6. The forEach() Method

Yeh arrays ka ek special method hai jo array ke har element ke liye ek function run karta hai.

const fruits = ["Apple", "Banana", "Mango"];

fruits.forEach(function(fruit, index) {
  console.log(index + ": " + fruit);
});
// Output:
// 0: Apple
// 1: Banana
// 2: Mango

Loops ka Sahi Use Kab Karein?

Key Takeaways

• Loops code ko repeat karne ka ek efficient tarika hai.
• for loop fixed iterations ke liye best hai.
• while loop condition-based execution ke liye best hai.
• for...of arrays ki values ke liye aur for...in objects ki keys ke liye use hota hai.