const assertions - array

index.ts

type Person = {
  id: number;
  name: string;
  scores: number[];
}
const people: Person[] = [
  { id: 1, name: "Bob", scores: [50, 45] },
  { id: 2, name: "Jane", scores: [70, 60] },
  { id: 3, name: "Paul", scores: [40, 75] }
]
function getPersonScores(id: number) {
  const person = people.filter(person => person.id === id)[0];
  return <const>[...person.scores];
}

const scores = getPersonScores(1);  // `scores` is of type `readonly number[]`
scores.push(50);                    // 💥 - Type error - Property 'push' does not exist on type 'readonly number[]'