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…

When working with conditionals types, within the “extends” expression, we can use the “infer” keyword to either get the type of the elements of an array, or even to get the return type of a function. We can use this to build a “FnReturnType” type, th…

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…

TypeScript & Advanced Types https://www.typescriptlang.org/docs/handbook/advanced-types.html#type-aliases TypeScript Types https://www.typescriptlang.org/docs/handbook/basic-types.html https://www.typescriptlang.org/docs/handbook/advanced-types.html…

Example 1: A never stop while loop return a never type. function run(): never { while(true){ let foo = "bar"; } } Example 2: Never run If block ; ) { let bar: never = foo; } You can use this to do exhaustive checks in union types. For example, l…

在学习TypeScript之前,我们需要先知道怎么才能让TypeScript写的东西正确的运行起来.有两种方式:使用Visual studio 和使用 NodeJs. 这里我选择的是NodeJs来编译TypeScript,因为我笔记本上的VS是2012的,在TypeScript的官网看到下载是TypeScript for VS2013和TypeScript for VS2015.额,顺带贴上TypeScript的官网,有需要的去下载. 然后使用NodeJs编译TypeScript的方法: //…

关于是否要在 PHP 8 中引入 Union Types 的投票已于近日结束,投票结果显示有 61 名 PHP 开发组成员投了赞成票,5 名投了反对票. 还留意到鸟哥在投票中投了反对票~) 因此根据投票结果,官方已确认将会在 PHP 8 中引入 Union Types 2.0. 关于 Union Types 的具体讨论可在 GitHub 查看,下面我们来简单了解一下 Union Types(联合类型). 根据官方的介绍,Union Types(联合类型)支持接收多个不同类型的值,而不仅仅是单一类…

Sometimes we might want to make a function more generic by having it accept a union of different types as an argument. Using the JavaScript “in” operator, we can test for the presence of different properties on the argument object, and TypeScript wil…

在接触 ts 相关代码的过程中,总能看到 interface 和 type 的身影.只记得,曾经遇到 type 时不懂查阅过,记得他们很像,相同的功能用哪一个都可以实现.但最近总看到他们,就想深入的了解一下他们. interface:接口 TypeScript 的核心原则之一是对值所具有的结构进行类型检查. 而接口的作用就是为这些类型命名和为你的代码或第三方代码定义契约. interface LabelledValue { label: string; } function printLabel…

键值对结构的对象 export type ValidationErrors = { [key: string]: any }; 联合类型(union type) export type HttpEvent<T> = HttpSentEvent | HttpHeaderResponse | HttpResponse<T>| HttpProgressEvent | HttpUserEvent<T>;…