How do I create an immutable Array?

Question

I have tried to write an Array that the script cannot mutate; not by adding or popping elements from or to the Array. I tried to do something like this:

const arr = [30, 20, 10]

but when I tried to add an element to the Array it works.

Can someone please can show me how to define an array that cannot change

Answer 1

You're looking for Object.freeze()

However, you should note that entries that are themselves Objects can still be modified, unless they are also frozen

const arr = [30, 20, 10, {name: 'Tom', age: 54}, [0]];
Object.freeze(arr);

// arr.push(10); // Uncaught TypeError: Cannot add property 3, object is not extensible
// arr.pop();    // Uncaught TypeError: Cannot delete property '2' of [object Array]

arr[0] = 5;

arr[3].name = 'Modified';
arr[4][0] = 'Modified';

console.log(arr);