JavaScript Loops & Iteration

// Basic for loop
for (let i = 0; i < 5; i++) {
    console.log(`Iteration ${i}`);
}

// For loop with array
const fruits = ['apple', 'banana', 'orange', 'grape'];
for (let i = 0; i < fruits.length; i++) {
    console.log(`Fruit ${i + 1}: ${fruits[i]}`);
}

// For...in loop (for object properties)
const person = {
    name: 'John',
    age: 30,
    city: 'NYC'
};

for (let key in person) {
    console.log(`${key}: ${person[key]}`);
}

// For...of loop (for iterable values)
const colors = ['red', 'green', 'blue'];
for (let color of colors) {
    console.log(`Color: ${color}`);
}

// For...of with strings
const message = 'Hello';
for (let char of message) {
    console.log(`Character: ${char}`);
}

// Nested for loops
for (let i = 1; i <= 3; i++) {
    for (let j = 1; j <= 3; j++) {
        console.log(`i=${i}, j=${j}`);
    }
}

// For loop with break
for (let i = 0; i < 10; i++) {
    if (i === 5) {
        break; // Exit loop when i equals 5
    }
    console.log(i);
}

// For loop with continue
for (let i = 0; i < 10; i++) {
    if (i % 2 === 0) {
        continue; // Skip even numbers
    }
    console.log(`Odd number: ${i}`);
}

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

// While loop with condition
let password = 'secret123';
let attempts = 0;
const maxAttempts = 3;

while (attempts < maxAttempts) {
    const input = prompt('Enter password:');
    if (input === password) {
        console.log('Access granted!');
        break;
    } else {
        attempts++;
        console.log(`Attempt ${attempts} failed. ${maxAttempts - attempts} attempts remaining.`);
    }
}

if (attempts >= maxAttempts) {
    console.log('Access denied. Too many failed attempts.');
}

// Do-while loop (executes at least once)
let number = 1;
do {
    console.log(`Number: ${number}`);
    number *= 2;
} while (number < 10);

// While loop for data processing
let data = [1, 2, 3, 4, 5];
let index = 0;
let sum = 0;

while (index < data.length) {
    sum += data[index];
    index++;
}

console.log(`Sum: ${sum}`);

// While loop with array modification
let numbers = [1, 2, 3, 4, 5];
let i = 0;

while (i < numbers.length) {
    if (numbers[i] % 2 === 0) {
        numbers.splice(i, 1); // Remove even numbers
    } else {
        i++;
    }
}

console.log('Odd numbers only:', numbers);

// Array forEach method
const numbers = [1, 2, 3, 4, 5];

numbers.forEach((number, index) => {
    console.log(`Number ${index + 1}: ${number}`);
});

// forEach with objects
const users = [
    { name: 'John', age: 30 },
    { name: 'Jane', age: 25 },
    { name: 'Bob', age: 35 }
];

users.forEach((user, index) => {
    console.log(`User ${index + 1}: ${user.name} (${user.age})`);
});

// Map method (creates new array)
const doubled = numbers.map(num => num * 2);
console.log('Doubled numbers:', doubled);

const userNames = users.map(user => user.name);
console.log('User names:', userNames);

// Filter method
const evenNumbers = numbers.filter(num => num % 2 === 0);
console.log('Even numbers:', evenNumbers);

const adults = users.filter(user => user.age >= 30);
console.log('Adults:', adults);

// Reduce method
const total = numbers.reduce((sum, num) => sum + num, 0);
console.log('Total:', total);

const oldestUser = users.reduce((oldest, user) => 
    user.age > oldest.age ? user : oldest
);
console.log('Oldest user:', oldestUser);

// Find method
const firstEven = numbers.find(num => num % 2 === 0);
console.log('First even number:', firstEven);

const john = users.find(user => user.name === 'John');
console.log('John:', john);

// Some and Every methods
const hasEven = numbers.some(num => num % 2 === 0);
console.log('Has even numbers:', hasEven);

const allAdults = users.every(user => user.age >= 18);
console.log('All adults:', allAdults);

// For...of with different iterables
// Arrays
for (let num of numbers) {
    console.log(num);
}

// Strings
for (let char of 'Hello') {
    console.log(char);
}

// Sets
const uniqueNumbers = new Set([1, 2, 2, 3, 3, 4]);
for (let num of uniqueNumbers) {
    console.log(num);
}

// Maps
const userMap = new Map([
    ['john', { name: 'John', age: 30 }],
    ['jane', { name: 'Jane', age: 25 }]
]);

for (let [key, value] of userMap) {
    console.log(`${key}: ${value.name}`);
}

// Exercise: Build a Number Guessing Game
function numberGuessingGame() {
    const secretNumber = Math.floor(Math.random() * 100) + 1;
    let attempts = 0;
    const maxAttempts = 10;
    
    console.log('Welcome to the Number Guessing Game!');
    console.log('I'm thinking of a number between 1 and 100.');
    
    while (attempts < maxAttempts) {
        attempts++;
        const guess = parseInt(prompt(`Attempt ${attempts}/${maxAttempts}: Enter your guess:`));
        
        if (isNaN(guess)) {
            console.log('Please enter a valid number.');
            continue;
        }
        
        if (guess === secretNumber) {
            console.log(`Congratulations! You guessed it in ${attempts} attempts!`);
            return;
        } else if (guess < secretNumber) {
            console.log('Too low! Try again.');
        } else {
            console.log('Too high! Try again.');
        }
    }
    
    console.log(`Game over! The number was ${secretNumber}.`);
}

// Exercise: Build a Data Processing System
function processData(data) {
    const results = {
        total: 0,
        average: 0,
        min: Infinity,
        max: -Infinity,
        evenCount: 0,
        oddCount: 0,
        positiveCount: 0,
        negativeCount: 0
    };
    
    // Process each number
    for (let num of data) {
        results.total += num;
        
        if (num < results.min) results.min = num;
        if (num > results.max) results.max = num;
        
        if (num % 2 === 0) {
            results.evenCount++;
        } else {
            results.oddCount++;
        }
        
        if (num > 0) {
            results.positiveCount++;
        } else if (num < 0) {
            results.negativeCount++;
        }
    }
    
    results.average = results.total / data.length;
    
    return results;
}

// Exercise: Build a Pattern Generator
function generatePattern(rows) {
    for (let i = 1; i <= rows; i++) {
        let pattern = '';
        for (let j = 1; j <= i; j++) {
            pattern += '* ';
        }
        console.log(pattern);
    }
}

function generateNumberPattern(rows) {
    for (let i = 1; i <= rows; i++) {
        let pattern = '';
        for (let j = 1; j <= i; j++) {
            pattern += j + ' ';
        }
        console.log(pattern);
    }
}

// Test the functions
const sampleData = [1, -2, 3, -4, 5, 6, -7, 8, 9, -10];
const stats = processData(sampleData);
console.log('Data Statistics:', stats);

console.log('Star Pattern:');
generatePattern(5);

console.log('Number Pattern:');
generateNumberPattern(5);