JavaScript Array Search

Types of Search Methods

🔹 Finding Element Position

Methods to find where elements are located in arrays:

let colors = ["red", "blue", "green", "blue", "yellow"];

// indexOf() - Find first occurrence
console.log(colors.indexOf("blue")); // 1
console.log(colors.indexOf("purple")); // -1 (not found)

// lastIndexOf() - Find last occurrence
console.log(colors.lastIndexOf("blue")); // 3

// findIndex() - Find using a condition
let numbers = [10, 20, 30, 40, 50];
let index = numbers.findIndex(num => num > 25);
console.log(index); // 2 (first number > 25 is at index 2)

// findIndex() with objects
let people = [
    {name: "John", age: 25},
    {name: "Jane", age: 30},
    {name: "Bob", age: 35}
];
let personIndex = people.findIndex(person => person.name === "Jane");
console.log(personIndex); // 1

🔹 Checking if Elements Exist

Methods to check if elements are present in arrays:

let fruits = ["apple", "banana", "orange", "grape"];

// includes() - Check if element exists (returns true/false)
console.log(fruits.includes("banana")); // true
console.log(fruits.includes("mango")); // false

// Case-sensitive check
console.log(fruits.includes("Apple")); // false (capital A)

// some() - Check if at least one element passes a test
let numbers = [1, 3, 5, 8, 9];
let hasEvenNumber = numbers.some(num => num % 2 === 0);
console.log(hasEvenNumber); // true (8 is even)

// every() - Check if all elements pass a test
let allPositive = numbers.every(num => num > 0);
console.log(allPositive); // true (all numbers are positive)

let allEven = numbers.every(num => num % 2 === 0);
console.log(allEven); // false (not all numbers are even)

🔹 Getting Elements

Methods to retrieve actual elements from arrays:

let students = [
    {name: "Alice", grade: 85},
    {name: "Bob", grade: 92},
    {name: "Charlie", grade: 78},
    {name: "Diana", grade: 96}
];

// find() - Get first element that matches condition
let topStudent = students.find(student => student.grade > 90);
console.log(topStudent); // {name: "Bob", grade: 92}

// find() returns undefined if nothing found
let failingStudent = students.find(student => student.grade < 60);
console.log(failingStudent); // undefined

// filter() - Get all elements that match condition
let goodStudents = students.filter(student => student.grade >= 85);
console.log(goodStudents); 
// [{name: "Alice", grade: 85}, {name: "Bob", grade: 92}, {name: "Diana", grade: 96}]

// Simple array example
let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
let evenNumbers = numbers.filter(num => num % 2 === 0);
console.log(evenNumbers); // [2, 4, 6, 8, 10]

🔹 Advanced Search Techniques

More complex ways to search through arrays:

// Search with multiple conditions
let products = [
    {name: "Laptop", price: 999, category: "Electronics"},
    {name: "Book", price: 15, category: "Education"},
    {name: "Phone", price: 699, category: "Electronics"},
    {name: "Pen", price: 2, category: "Office"}
];

// Find cheap electronics
let cheapElectronics = products.filter(product => 
    product.category === "Electronics" && product.price < 800
);
console.log(cheapElectronics); // [{name: "Phone", price: 699, category: "Electronics"}]

// Search in strings (case-insensitive)
let names = ["John", "jane", "MIKE", "sarah"];
let searchTerm = "ja";
let matchingNames = names.filter(name => 
    name.toLowerCase().includes(searchTerm.toLowerCase())
);
console.log(matchingNames); // ["jane"]

// Search with regular expressions
let emails = ["[email protected]", "[email protected]", "[email protected]"];
let gmailUsers = emails.filter(email => email.includes("@gmail.com"));
console.log(gmailUsers); // ["[email protected]"]

// Custom search function
function searchArray(array, searchValue) {
    return array.filter(item => 
        String(item).toLowerCase().includes(String(searchValue).toLowerCase())
    );
}

let fruits = ["Apple", "Banana", "Orange", "Grape"];
console.log(searchArray(fruits, "ap")); // ["Apple", "Grape"]

🔹 Practical Search Examples

Real-world applications of array search methods:

// User management system
let users = [
    {id: 1, username: "john_doe", email: "[email protected]", active: true},
    {id: 2, username: "jane_smith", email: "[email protected]", active: false},
    {id: 3, username: "bob_wilson", email: "[email protected]", active: true}
];

// Find user by ID
function findUserById(id) {
    return users.find(user => user.id === id);
}
console.log(findUserById(2)); // {id: 2, username: "jane_smith", ...}

// Check if username is taken
function isUsernameTaken(username) {
    return users.some(user => user.username === username);
}
console.log(isUsernameTaken("john_doe")); // true

// Get all active users
let activeUsers = users.filter(user => user.active);
console.log(activeUsers.length); // 2

// Shopping cart search
let cart = ["laptop", "mouse", "keyboard", "monitor"];

// Check if item is in cart
function isInCart(item) {
    return cart.includes(item.toLowerCase());
}
console.log(isInCart("Mouse")); // true (case-insensitive)

// Remove item from cart
function removeFromCart(item) {
    let index = cart.indexOf(item.toLowerCase());
    if (index > -1) {
        cart.splice(index, 1);
        return true;
    }
    return false;
}
console.log(removeFromCart("mouse")); // true
console.log(cart); // ["laptop", "keyboard", "monitor"]