While Loops in Javascript

Learn about whileloop in javascript with practical examples and code snippets.

Basic While Loop

Code

const cars = [
  { id: 1, name: "Nexon", brand: "Tata", make: "2017", rating: 2 },
  { id: 2, name: "Verna", brand: "Hyundai", make: "2008", rating: 4 },
  { id: 3, name: "Bolero", brand: "Mahindra", make: "2012", rating: 5 },
  { id: 4, name: "Baleno", brand: "Maruti", make: "2022", rating: 4 },
  { id: 5, name: "Seltos", brand: "Kia", make: "2011", rating: 3 },
  { id: 6, name: "G-class", brand: "Mercedes", make: "2024", rating: 5 }
];
let i = 0;
while (i < cars.length) {
  console.log(`${cars[i].brand} -> ${cars[i].name}`);
  i++;
}

While Loop with Condition

Output: Count: 0, 1, 2, 3, 4.

Code

let count = 0;
while (count < 5) {
  console.log(`Count: ${count}`);
  count++;
}

While Loop with Break

Code

let index = 0;
while (index < cars.length) {
  if (cars[index].rating === 5) {
    console.log(`Found perfect car: ${cars[index].name}`);
    break; // Exit loop
  }
  index++;
}

While Loop with Continue

Code

let j = 0;
while (j < cars.length) {
  j++;
  if (cars[j - 1].rating < 4) {
    continue; // Skip to next iteration
  }
  console.log(`High rated: ${cars[j - 1].name}`);
}

Infinite Loop Prevention

Some condition that might never be true.

Code

let counter = 0;
const maxIterations = 100; // Safety limit
while (counter < maxIterations) {
  if (someCondition()) {
    break;
  }
  counter++;
}

While Loop for Input Validation

In real scenario: input = prompt("Enter your name:");.

Code

function getUserInput() {
  let input;
  while (!input || input.trim() === '') {
    input = "Kuldeep"; // Simulated
  }
  return input;
}

While Loop for Processing Queue

Code

const queue = [1, 2, 3, 4, 5];
while (queue.length > 0) {
  const item = queue.shift();
  console.log(`Processing: ${item}`);
}

Nested While Loops

Common Use Cases 1.

Reading until end of data 2.

Retry logic 3.

Code

let row = 0;
while (row < 3) {
  let col = 0;
  while (col < 3) {
    console.log(`[${row}][${col}]`);
    col++;
  }
  row++;
}
let dataIndex = 0;
while (dataIndex < data.length) {
  processData(data[dataIndex]);
  dataIndex++;
}
let attempts = 0;
const maxAttempts = 3;
while (attempts < maxAttempts) {
  if (tryOperation()) {
    break;
  }
  attempts++;
}
let gameRunning = true;
while (gameRunning) {
  updateGame();
  if (gameOver()) {
    gameRunning = false;
  }
}

---

Summary

Understanding whileloop is essential for mastering javascript. Practice these examples and experiment with variations to deepen your understanding.

Key Takeaways

• whileloop is a fundamental concept in javascript
• Practice with these examples to build confidence
• Experiment with variations to explore edge cases
• Understanding whileloop will help you in technical interviews