typescript-3.7.5.tar.gz

TypeScript 3.7.5 Strict

TypeScript 3.7.5

Are you using TypeScript, but feel like you’re not making the most out of it? Do you find some advanced TypeScript concepts confusing? Do you get lost looking at complex type errors?

If you answered “yes” to any of these questions, then this course is for you! It introduces you to the world of advanced TypeScript concepts including: compiler flags for catching more errors, generic types, and how to compose types with discriminated unions. 

After finishing this course, you’ll feel more confident in your TypeScript skills. You will be able to write types that detect whole classes of possible runtime errors at compile time. Typing even the most untypeable JavaScript code will be a no brainer for you, and you’ll be fluent in TypeScript error messages.

Advanced TypeScript Masterclass

## Defining optionality

As you saw in the previous lesson, strict null checks force you to explicitly distinguish between values that can be `null` or `undefined` and those that cannot be. You already saw how to do this with a union type.

```typescript
interface Person {
  name: string;
}

let nullableJohn: Person | null;
let maybeUndefinedBob: Person | undefined;
let ambiguoslyEmptyAlice: Person | null | undefined;
```

# Defining optionality

As you saw in the previous lesson, strict null checks force you to explicitly distinguish between values that can be `null` or `undefined` and those that cannot be. You already saw how to do this with a union type.

```typescript
interface Person {
  name: string;
}

let nullableJohn: Person | null;
let maybeUndefinedBob: Person | undefined;
let ambiguoslyEmptyAlice: Person | null | undefined;
```

This lesson discusses how TypeScript analyses optional values in `if` statements when the `strictNullChecks` flag is enabled.

Strict types

Generics

Composing types

Advanced types

TypeScript in practice

Conclusion

Optionality

Defining optionality