AngularJS: How to fix the error 'Cannot assign to 'bar' because it is a constant or a read-only property.'

Question

Given the following code:
```typescript
type Foo = {
    readonly bar: number;
    bas: number;
}

let foo: Foo = { bar: 123, bas: 456 };

foo.bar = 18;
foo.bas = 10;
```
What will this code produce?

Accepted Answer

Cannot assign to 'bar' because it is a constant or a read-only property.

Answer

{"bar":123,"bas":10}

Answer

{"bar":18,"bas":10}

Question from the Angular 4 (legacy) test

AngularJS: How to fix the error 'Cannot assign to 'bar' because it is a constant or a read-only property.'