Concept

Arrays are an important part of JavaScript programming, allowing you to store and manage multiple values in a single data structure.

Declare and initialize an array

In JavaScript, we can declare and initialize an array using square brackets [].

let numbers = [1, 2, 3, 4, 5];
let fruits = ["apple", "banana", "orange"];

In the example above, we created an array called numbers with 5 elements ranging from 1 to 5, and an array called fruits with 3 elements representing different types of fruits.

Accessing and editing elements in an array

To access an element in an array, we can use the index of that element. Indexes in JavaScript start from 0.

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

console.log(numbers[0]); // Kết quả: 1
console.log(numbers[2]); // Kết quả: 3

We can also edit the value of an element in the array by assigning a new value to that element.

let numbers = [1, 2, 3, 4, 5];
numbers[2] = 10;

console.log(numbers); // Kết quả: [1, 2, 10, 4, 5]

Array methods

JavaScript provides many useful methods for manipulating arrays. Here are some popular methods:

• push(): Add an element to the end of the array.
• pop(): Remove the last element from the array and return the removed element.
• shift(): Remove the first element from the array and return the removed element.
• unshift(): Add an element to the beginning of the array.
• slice(): Copy a portion of the array and return a new array.
• splice(): Modify the content of the array by deleting, adding, or replacing elements.

Here is an example of how to use some of these methods:

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

fruits.push("grape"); // Thêm "grape" vào cuối mảng
fruits.pop(); // Xóa phần tử cuối cùng khỏi mảng

fruits.shift(); // Xóa phần tử đầu tiên khỏi mảng
fruits.unshift("kiwi"); // Thêm "kiwi" vào đầu mảng

let slicedFruits = fruits.slice(1, 3); // Sao chép các phần tử từ chỉ số 1 đến 2 (không bao gồm chỉ số 3)
fruits.splice(1, 2, "pear", "pineapple"); // Xóa 2 phần tử từ chỉ số 1 và thay thế bằng "pear" và "pineapple"

console.log(fruits); // Kết quả: ["kiwi", "pear", "pineapple"]
console.log(slicedFruits); // Kết quả: ["pear", "pineapple"]

Looping through elements in an array

To iterate through each element in the array, we can use a for loop or a forEach loop.

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

for (let i = 0; i < numbers.length; i++) {
  console.log(numbers[i]);
}

numbers.forEach(function(number) {
  console.log(number);
});

Both of these methods will display the elements in the numbers array on the console.