Difference between const and readonly in typescript

Question

Constant vs readonly in typescript

Declaring a variable as readonly will not allow us to override even if they are public properties.

How const beha

Answer 1

One of the key difference between const and readonly is in how it works with the array. (appart form already ans diff) You have to use ReadonlyArray while working with Array, where T is generic type(google it for more).

when u declare any array as const, you can perform operations on array which may change the array elements. for ex.

const Arr = [1,2,3];

Arr[0] = 10;   //OK
Arr.push(12); // OK
Arr.pop(); //Ok

//But
Arr = [4,5,6] // ERROR

But in case of ReadonlyArray you can not change the array as shown above.

arr1 : ReadonlyArray = [10,11,12];

arr1.pop();    //ERROR
arr1.push(15); //ERROR
arr1[0] = 1;   //ERROR