JavaScript Arrays with const

In JavaScript, declaring an array with const means the reference to the array cannot be changed, but the contents of the array remain mutable.

• You can modify, add, or remove elements.
• You cannot reassign the array to a new one.

Example 1: Modifying Array Contents

const fruits = ["Apple", "Banana", "Mango"];

// Modify elements
fruits[0] = "Orange";

// Add new element
fruits.push("Kiwi");

console.log(fruits);
// Output: ["Orange", "Banana", "Mango", "Kiwi"]

// Reassigning the array is NOT allowed
// fruits = ["Pineapple"]; // TypeError

Example 2: Using Array Methods

const numbers = [1, 2, 3, 4];

numbers.pop();   // removes 4
numbers.push(5); // adds 5

console.log(numbers); // [1, 2, 3, 5]

Important Notes

Block Scope

const arrays are block-scoped, like let.

if (true) {
    const temp = [1, 2, 3];
    console.log(temp); // [1, 2, 3]
}
// console.log(temp); // Error: temp is not defined

Must Be Initialized

A const array must be assigned a value during declaration.

// const arr; // Error
const arr = []; // Correct

Making an Array Immutable

const does not make the array itself immutable. Use Object.freeze() to prevent modifications:

const nums = Object.freeze([1, 2, 3]);

nums.push(4); // Error in strict mode

Object.freeze() is shallow. Objects inside the array can still be modified:

const arr = Object.freeze([{name: "John"}]);
arr[0].name = "Doe"; // Allowed