TypeScript 2.0 introduced the readonly modifier which can be added to a property or index signature declaration. It helps prevent against unintended property assignments. This lesson gives various use cases for readonly and shows what the generated J…

Typescript 2.5 adds JSDoc type assertion support for javascript file via ts-check service. First of all, you should make sure you have typescript@2.5 install: sudo npm i -g typescript@2.5 Then add @ts-check to the top of js file: // @ts-check This te…

We will look at how we can use mapped types, conditional types, self-referencing types and the “infer” keyword to create a reusable generic type that traverses down the properties of an object and marks of all them as read-only. This is especially us…

The keyof operator produces a union type of all known, public property names of a given type. You can use it together with lookup types (aka indexed access types) to statically model dynamic property access in the type system. Take away: 1. extends 2…

Mapped types are a powerful and unique feature of TypeScript's type system. They allow you to create a new type by transforming all properties of an existing type according to a given transformation function. In this lesson, we'll cover mapped types…

Using the optional “+” sign together with mapped type modifiers, we can create more explicit and readable type declarations. We can also use the “-” (minus) sign to remove optional declarations from properties. For example, we have an interface: inte…

TypeScript’s discriminated union types (aka tagged union types) allow you to model a finite set of alternative object shapes in the type system. The compiler helps you introduce fewer bugs by only exposing properties that are known to be safe to acce…

Aspect Oriented Programming, AOP, allows to reuse logic across an entire app in a very neat way, decoupling it from the business logic. Kaop-ts bring us decorators in order to apply AOP. This lesson will show you how you can move cache and exception…

This lesson introduces the --strictNullChecks compiler option and explains how non-nullable types differ from nullable types. It also illustrates how you can write safer code by being explicit about null and undefined in the type system. First of all…

文档: https://angular.io/guide/template-syntax#event-binding The Angular compiler may reject these bindings with errors like this one: content_copyUncaught Error: Template parse errors: Can't bind to 'hero' since it isn't a known property of 'app-hero-…