typescript

Question 1

What is the goal of typescript?

Answer 1

The goal of TypeScript is to be a static typechecker for JavaScript programs - in other words, a tool that runs before your code runs (static) and ensures that the types of the program are correct (typechecked).

Question 2

JavaScript provides language primitives such as string and number, what does typescript do with these primitives that javascript doesn’t?

Answer 2

It checks that you’ve consistently assigned these throughout your code. It stops a variables type being altered throughout the lifetime of the variable.

Question 3

What does “types by inference” mean?

Answer 3

TypeScript knows the JavaScript language and will generate types for you in many cases. For example in creating a variable and assigning it to a particular value, TypeScript will use the value as its type.

let helloWorld = “Hello World”;

the inferred type will be string
– let helloWorld: string

Question 4

How would you create an object with an inferred type which includes name: string and id: number ?

Answer 4

const user = {
  name: "Hayes",
  id: 0,
};

Question 5

How would you explicitly describe an object’s shape ?

Answer 5

using an interface declaration:

interface User {
name: string;
id: number;
}

You can then declare that a JavaScript object conforms to the shape of your new interface by using syntax like : TypeName after a variable declaration:

const user: User = {
name: “Hayes”,
id: 0,
};

Question 6

There is already a small set of primitive types available in JavaScript: boolean, bigint, null, number, string, symbol, and undefined, which you can use in an interface. TypeScript extends this list with a few more, such as … ?

Answer 6

• • any (allow anything),
• • unknown (ensure someone using this type declares what the type is),
• • never (it’s not possible that this type could happen),
• • void (a function which returns undefined or has no return value).