JavaScript Assignment 08

1. Write short notes on the following Array methods with code examples

• filter()
• some()
• every()
• map()
• forEach()
• reduce()
• indexOf()

Ans.

1. filter()

• Creates a new array with elements that pass a test (returns true).
• Doesn’t change the original array.

        let numbers = [10, 25, 30, 45];
        let result = numbers.filter(num => num > 20);
        console.log(result); // [25, 30, 45]

2. some()

• Checks if at least one element passes a condition.
• Returns true or false.

let nums = [3, 6, 8];
console.log(nums.some(num => num > 5)); // true

3. every()

• Checks if all elements satisfy a condition.
• Returns true or false.

let nums2 = [2, 4, 6];
console.log(nums2.every(num => num % 2 === 0)); // true

4. map()

• Creates a new array by applying a function to each element.
• Doesn’t change the original array.

let arr = [1, 2, 3];
let doubled = arr.map(x => x * 2);
console.log(doubled); // [2, 4, 6]

5. forEach()

• Executes a function once for each array element.
• Does not return a new array.

let fruits = ["apple", "banana", "cherry"];
fruits.forEach(fruit => console.log(fruit.toUpperCase()));
// APPLE
// BANANA
// CHERRY

6. reduce()

• Reduces the array to a single value (like sum, product).
• Takes a callback with an accumulator and current value.

let numbers2 = [1, 2, 3, 4];
let sum = numbers2.reduce((acc, curr) => acc + curr, 0);
console.log(sum); // 10

7. indexOf()

• Returns the first index of a value in the array.
• Returns -1 if not found.

let colors = ["red", "green", "blue", "green"];
console.log(colors.indexOf("green")); // 1
console.log(colors.indexOf("yellow")); // -1

2. https://javascript-array-methods-quiz.netlify.app/