Conditional types take generics one step further and allow you to test for a specific condition, based on which the final type will be determined. We will look at how they work on a basic level and then leverage their power to allocate function types…

前言 在第二小节中,我们讨论了利用TypeScript创建Web项目的实现,在本下节,我们讨论一下如何结合React创建一个具备TypeScript类型的应用项目. 准备 Webpack配置在第二小节项目的基础上做了一些修改, 添加React相关依赖:react.react-dom.@types/react 和@types/react-dom 修改Webpack配置文件 修改webpack.base.config.js,其余文件和第二小节保持一致,修改如下: const HtmlWebpackP…

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…

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…

Sometimes we want our function arguments to be able to accept more than 1 type; e.g. a string or an array. This lesson will show us how to assign more than 1 type to a variable with Typescript union types and type aliases. type types = string | boole…

Some functions may have different return types depending on the types of the arguments with which they’re invoked. Using TypeScript’s function overloads, you can create an overload for each allowed combination of parameter and return types. This way,…

Decorators are a powerful feature of TypeScript that allow for efficient and readable abstractions when used correctly. In this lesson we will look at how we can use decorators to initialize properties of a class to promises that will make GET reques…

type DigitValidator = (char) => boolean; -]{}/.test(char); export const digitValidators: {[key: string]: DigitValidator} = { ': numericValidator }; We can use 'type' keyword to define a function type. 'digitValidators', is a mapping object, return a…

前言 Union Type和Intersection Type都是将多个类型结合起来的一个等价的"类型",它们并非是实际存在的类型. Union Type Union type(联合类型)使用比特或运算符|进行构造: A | B | C 注意:用|符号来构造Union Type类型只是Java语言的规定,|在这里不代表比特或的含义. 上例中,A | B | C是一个Union type,Union type的含义就是"或",只要满足其中一个即可. 实例:捕获多个异常…

代码如下: var query = from s in db.LoginUserServices join ss in db.Services on s.ServiceType equals ss.Code into s_ss_join from s_ss in s_ss_join.DefaultIfEmpty() where s.LoginUserID.Equals(LoginUserID) select new { // ServiceType = s.ServiceType, Servic…