Questions

Let's have a go at some questions on advanced types:

1. We have an interface that represents a course result, as follows:

interface ICourseMark {
  courseName: string;
  grade: string;
}

We can use this interface as follows:

const geography: ICourseMark = {
  courseName: "Geography",
  grade: "B"
} 

The grades can only be A, B, C, or D. How can we create a stronger typed version of the grade property in this interface?

2. We have the following functions that validate that numbers and strings are populated with a value:

function isNumberPopulated(field: number): boolean {
  return field !== null && field !== undefined;
}

function isStringPopulated(field: string): boolean {
  return field !== null && field !== undefined && field !== "";
}

How can we combine these into a single function called isPopulated with signature overloads...