JavaScript Arrays and Array Methods Documentation

Arrays in JavaScript are used to store multiple values in a single variable. They are a special type of object that allows you to work with ordered collections of data.

Creating Arrays

Arrays can be created using array literals or the Array constructor.

Example Code

let arr = [1, 2, 3, 4, 5, 6]; // Array literal
arr[3] = 8; // Modifying the value at index 3

Explanation

• arr is an array containing six elements. The value at index 3 is modified to 8.

Array Methods

JavaScript provides various methods to manipulate arrays. Here are some commonly used methods:

Example Code

let fastFood = ["Maggie", "Momos", "Burger"]; // Array of fast food items
 
console.log(fastFood); // Outputs: ["Maggie", "Momos", "Burger"]
 
console.log(fastFood.indexOf("Momos")); // Outputs: 1 (index of "Momos")
console.log(fastFood.includes("Pizza")); // Outputs: false (checks if "Pizza" is in the array)
 
fastFood.push("Pizza"); // Adds "Pizza" to the end of the array
fastFood.unshift("Fried Momos"); // Adds "Fried Momos" to the beginning of the array
 
fastFood.pop(); // Removes the last element ("Pizza")
fastFood.shift(); // Removes the first element ("Fried Momos")
 
console.log(fastFood.length); // Outputs: 2 (length of the array)

Explanation

• indexOf("Momos") returns the index of the first occurrence of "Momos" in the array.
• includes("Pizza") checks if "Pizza" is present in the array and returns false.
• push("Pizza") adds "Pizza" to the end of the array.
• unshift("Fried Momos") adds "Fried Momos" to the beginning of the array.
• pop() removes the last element from the array.
• shift() removes the first element from the array.
• length property returns the number of elements in the array.

Combining Arrays

You can combine arrays using various methods, including the spread operator and the concat() method.

Example Code

let homeFood = ["Roti", "Sabji", "Salad"];
// let arr2 = fastFood + homeFood; // Concatenation using + operator
// fastFood.push(homeFood); // Adds the entire home Food array as a single element
// let arr2 = fastFood.concat(homeFood); // Concatenation using concat method
let arr2 = [...fastFood, "You are Coder", ...homeFood, ...arr]; // Using spread operator to combine arrays

Explanation

• The spread operator (...) allows you to expand elements of an array into another array, making it easy to combine multiple arrays and add additional elements.

Array Slicing and Splicing

JavaScript provides methods to extract or remove elements from arrays.

Example Code

let arr3 = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
// let tukda = arr3.slice(2, 6); // Extracts elements from index 2 to 5
let tukda = arr3.splice(2, 4); // Removes 4 elements starting from index 2
 
console.log(tukda); // Outputs the removed elements
console.log(arr3); // Outputs the modified array
 
console.log(arr3.reverse()); // Reverses the order of elements in the array

Explanation

• slice(start, end) returns a shallow copy of a portion of an array into a new array object, without modifying the original array.
• splice(start, deleteCount) changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.
• reverse() reverses the elements of the array in place.

Creating and Filling Arrays

You can create arrays of a specific length and fill them with a value.

Example Code

let arr4 = new Array(9).fill(null); // Creates an array of length 9 filled with null
console.log(arr4); // Outputs: [null, null, null, null, null, null, null, null, null]

Explanation

• new Array(length) creates an array with the specified length, and fill(value) fills all elements of the array with the specified value.

Joining Array Elements

You can join all elements of an array into a string using the join() method.

Example Code

let joined = arr3.join("."); // Joins elements of arr3 with a dot separator
console.log(joined); // Outputs: "10.20.30.40.50.60.70.80.90.100"

Explanation

• join(separator) creates and returns a new string by concatenating all of the elements in an array, separated by the specified separator.

Conclusion

Arrays are a fundamental part of JavaScript, allowing you to store and manipulate collections of data efficiently. Understanding array methods is essential for effective programming in JavaScript.