TypeScript & as & Type Assertion Type Assertion (as) That is not vanilla JavaScript, it is TypeScript. As any means consider the typed object as a plain untyped javascript object. The as keyword is a Type Assertion in TypeScript which tells the co…

The DOM can be a bit tricky when it comes to typing. You never really know exactly what you're going to get, so you have to educate your codebase into what you know you're using. This is done using Type Assertion where TypeScript types know they're a…

The "any" type can be very useful, especially when adding types to an existing JavaScript codebase, but it can also lead to lots of runtime errors, as it provides no type-checking. The "unknown" type on the other hand, restricts develo…

TypeScript tries to infer as much about your code as it can. But sometimes there really is not enough context for it to infer reliably. If it tried to do such inference it would potentially result in more nuisance than help. So instead it infers the…

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…

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…

项目初始化:采用TypeScript 我们的版本是: $ node --version v8.5.0 $ npm --version 5.5.1 npm版本升级了,因为npm最近带来了新特性,本地会生成package-lock.json,能 提高一些性能,想知道更多的,可以google一下. 创建目录初始结构: $ mkdir pickle $ cd pickle $ touch index.html $ touch index.ts $ touch webpack.config.js 初始化p…

1.什么是TypeScript (本人用自己的理解梳理了一下,不代表官方意见) TypeScript:Type+ECMAScript6 TypeScript是一种预处理编程语言,遵循es6标准规范,在ES6的基础之上增加了一个类型的语法概念 Javascript是弱类型语言,只有在代码执行过程中才会发现问题:TypeScript是强类型语言,一旦申明不能修改,强类型的校验可以避免开发过程中的低级错误 报错示范: 正常情况: 错误示范: 报错原因:对象属性申明了类型,所以不能为空对象 正常情况:…

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…

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…