If you're a library author, it's useful to expose your public types as interfaces, to allow your consumers to extend them if needed. For example: To resolve the issues, we can do : // typings.d.ts interface JQuery { hideChildren(): JQuery }…

TypeScript constructor public cause duplicate bug constructor public const log = console.log; // constructor public class TS4x { constructor(public version: string, public author: string) { this.version = version; this.author = author; this.init(); }…

A literal type is a type that represents exactly one value, e.g. one specific string or number. You can combine literal types with union types to model a finite set of valid values for a variable. In this lesson, we explore the all kinds of literal t…

TypeScript Interface vs Types All In One TypeScript https://www.typescriptlang.org/docs/handbook/advanced-types.html https://www.typescriptlang.org/docs/handbook/interfaces.html interface https://www.tutorialsteacher.com/typescript/typescript-interfa…

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…

ypeScript 2.2 introduced the object, a type that represents any non-primitive type. It can be used to more accurately type methods such as Object.create. Don't confuse it with the Object type or {}, the empty object type, though! So one thing we need…

Lookup types, introduced in TypeScript 2.1, allow us to dynamically create types based on the property keys of an object. We'll use the function spyOn from Jest to illustrate how lookup types can type-safe function parameters. Considering this code:…

In JavaScript, many libraries use string arguments to change behavior. In this lesson we learn how Typescript catches string related errors at compile time by assigning a string literal as a type. type whiteList = "DOG" | "CAT" | "…

classes & public shorthand Also of note, the use of public on arguments to the constructor is a shorthand that allows us to automatically create properties with that name. http://www.typescriptlang.org/docs/handbook/typescript-in-5-minutes.html#class…

For example you have a TS app: enum PaylerPosition { Guard, Forward, Center } interface Player { name: string; position: PlayerPosition; } let kobe = { name: 'Kobe', position: PlayerPosition.Guard }; The problem for this piece of code is that, you ca…