const in Angular 2

If the variable foo is a const that points to an object — we can’t make foo point to another object later on:

const foo = {};
foo = {}; // TypeError: Assignment to constant variable.
But we can however mutate, make changes to, the object foo points to, like so:

const foo = {};
foo['prop'] = "Moo"; // This works!
console.log(foo);
If we want the value of foo to be immutable we have to freeze it using Object.freeze(…​).

When we freeze an object we can’t change it, we can’t add properties or change the values of properties, like so:

const foo = Object.freeze({});
foo.prop = 123;
console.log(foo.prop) // undefined