🔧 JavaScript Array Methods, String Methods, & Math.random()

let array = [10, 20, 30, 40, 50];

// Find the index of element 30
let index = array.indexOf(30);
console.log(index); // Output: 2

// Search for an element that is not in the array
index = array.indexOf(60);
console.log(index); // Output: -1

// Search starting from index 3
index = array.indexOf(30, 3);
console.log(index); // Output: -1 (30 is before index 3)

let array = [1, 2, 3, 4, 5];

// Create a new array from index 1 to 3 (4 is not included)
let newArray = array.slice(1, 4);
console.log(newArray); // Output: [2, 3, 4]

// Create a new array from index 2 to the end
let anotherArray = array.slice(2);
console.log(anotherArray); // Output: [3, 4, 5]

// Copy the entire array
let copyArray = array.slice();
console.log(copyArray); // Output: [1, 2, 3, 4, 5]

let array = ['Apple', 'Banana', 'Cherry'];

// Join elements with a comma (default separator)
let joined = array.join();
console.log(joined); // Output: 'Apple,Banana,Cherry'

// Join elements with a custom separator (e.g., a space)
let joinedWithSpace = array.join(' ');
console.log(joinedWithSpace); // Output: 'Apple Banana Cherry'

// Join elements with a custom separator (e.g., a dash)
let joinedWithDash = array.join('-');
console.log(joinedWithDash); // Output: 'Apple-Banana-Cherry'

let array = [1, 2, 3, 4, 5];

// Check if the array includes the number 3
let hasThree = array.includes(3);
console.log(hasThree); // Output: true

// Check if the array includes the number 6
let hasSix = array.includes(6);
console.log(hasSix); // Output: false

// Check if the array includes the number 3, starting from index 2
let hasThreeFromIndexTwo = array.includes(3, 2);
console.log(hasThreeFromIndexTwo); // Output: true (3 is present starting from index 2)

// Check if the array includes the number 3, starting from index 4
let hasThreeFromIndexFour = array.includes(3, 4);
console.log(hasThreeFromIndexFour); // Output: false (3 is not present starting from index 4)

let numbers = [1, 2, 3, 4, 5];

// Create a new array with each element doubled
let doubled = numbers.map(x => x * 2);
console.log(doubled); // Output: [2, 4, 6, 8, 10]

// Create a new array with the squares of each element
let squared = numbers.map(x => x ** 2);
console.log(squared); // Output: [1, 4, 9, 16, 25]

// Create a new array with element indexes as strings
let indexed = numbers.map((x, i) => `${i}: ${x}`);
console.log(indexed); // Output: ['0: 1', '1: 2', '2: 3', '3: 4', '4: 5']

let numbers = [1, 2, 3, 4, 5];

// Filter out elements less than 4
let filtered = numbers.filter(x => x >= 4);
console.log(filtered); // Output: [4, 5]

// Filter out odd numbers
let evenNumbers = numbers.filter(x => x % 2 === 0);
console.log(evenNumbers); // Output: [2, 4]

// Filter an array of objects
let people = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 35 }
];

// Filter people who are 30 or older
let adults = people.filter(person => person.age >= 30);
console.log(adults); // Output: [{ name: 'Bob', age: 30 }, { name: 'Charlie', age: 35 }]

let numbers = [1, 2, 3, 4, 5];

// Sum all elements in the array
let sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
console.log(sum); // Output: 15

// Find the maximum value in the array
let max = numbers.reduce((accumulator, currentValue) => Math.max(accumulator, currentValue));
console.log(max); // Output: 5

// Create an object counting occurrences of each number
let countOccurrences = numbers.reduce((accumulator, currentValue) => {
  accumulator[currentValue] = (accumulator[currentValue] || 0) + 1;
  return accumulator;
}, {});
console.log(countOccurrences); // Output: { '1': 1, '2': 1, '3': 1, '4': 1, '5': 1 }

let array = [1, 2, 3, 4, 5];

// Remove 2 elements starting from index 1
array.splice(1, 2); 
console.log(array); // Output: [1, 4, 5];

// Add elements starting from index 1
array.splice(1, 0, 'a', 'b'); 
console.log(array); // Output: [1, 'a', 'b', 4, 5];

let array = [2, 3, 4];

// Add elements to the beginning
array.unshift(0, 1);
console.log(array); // Output: [0, 1, 2, 3, 4]

let array = [1, 2, 3, 4, 5];

// Fill the entire array with the value 0
array.fill(0);
console.log(array); // Output: [0, 0, 0, 0, 0]

// Fill a part of the array with the value 7
array.fill(7, 1, 4);
console.log(array); // Output: [0, 7, 7, 7, 0]

let numbers = [4, 2, 5, 1, 3];

// Sort numbers in ascending order
numbers.sort((a, b) => a - b);
console.log(numbers); // Output: [1, 2, 3, 4, 5]

// Sort numbers in descending order
numbers.sort((a, b) => b - a);
console.log(numbers); // Output: [5, 4, 3, 2, 1]

// Sort strings
let strings = ['banana', 'apple', 'cherry'];
strings.sort();
console.log(strings); // Output: ['apple', 'banana', 'cherry']

let original = 'hello';
// Replace characters
let replaced = original.replace('e', 'a');
console.log(replaced); // Output: 'hallo'
console.log(original); // Output: 'hello' (original string remains unchanged)

let original = 'hello';
// Get a substring
let substring = original.substring(1, 4);
console.log(substring); // Output: 'ell'
console.log(original); // Output: 'hello' (original string remains unchanged)

let text = 'apple,banana,cherry';

// Split the string by commas
let fruits = text.split(',');
console.log(fruits); // Output: ['apple', 'banana', 'cherry']

// Split the string by commas with a limit of 2
let limitedFruits = text.split(',', 2);
console.log(limitedFruits); // Output: ['apple', 'banana']

// Split the string with no separator
let singleElementArray = text.split();
console.log(singleElementArray); // Output: ['apple,banana,cherry']

let text = 'Hello, World!';

// Get the character at index 7
let char = text.charAt(7);
console.log(char); // Output: 'W'

let text = 'Hello, World!';

// Get the Unicode code of the character at index 7
let code = text.charCodeAt(7);
console.log(code); // Output: 87 (Unicode for 'W')

let text = 'Hello, World!';

// Search for the first occurrence of 'World'
let index = text.search('World');
console.log(index); // Output: 7

// Search for a pattern using a regular expression
let regexIndex = text.search(/world/i); // Case-insensitive search
console.log(regexIndex); // Output: 7

let randomIndex = Math.floor(Math.random() * 5);
console.log(randomIndex); // Output: 0, 1, 2, 3, or 4

let randomNumber = Math.floor(Math.random() * 5) + 1;
console.log(randomNumber); // Output: 1, 2, 3, 4, or 5