Like many good solutions in programming, you achieve this by adding a layer of indirection. Specifically, what we can do here is add a table between action tags (i.e. “Example” and “Another”) and their respective payloads. type ActionPayloadTable = { “Example”: { example: true }, “Another”: { another: true }, } then what we can … Read more
The compiler will widen string literal type to string, unless some specific conditions are met as explained in github issues and PR, or const assertion is used for literal value. Const assertions appeared in TypeScript 3.4: const KeyToVal = { MyKey1: ‘myValue1’, MyKey2: ‘myValue2’, } as const; type Keys = keyof typeof KeyToVal; type Values … Read more
Let’s say you’re developing a package “A” that have @types/some-module package in devDependencies. For some reason you’re exporting the type from @types/some-module: import { SomeType } from ‘some-module’; export default class APackageClass { constructor(private config: SomeType) { // … } } Right now TypeScript consumers of package “A” are unable to guess what SomeType is, … Read more
Yes, you just need to wrap the interface into global declaration: declare global { interface Window { myCounter: number; } } Global scope can be augmented from modules using a declare global declarations More info here ** Make sure the file is treated as a module (has import or export statement, if not – you … Read more
@types is the new way to install the definitions in typescript 2.0. It unifies the management of definitions and packages. So that you do not need multiple tools and config files. Only going to need npm and package.json instead of having to have npm, package.json, typings, typings.json. It basically makes installing and managing definitions easier … Read more
The compiler doesn’t understand the concept of “nested discriminated unions”. A type is a discriminated union if the members of the union share a common “discriminant” property. A discriminant property is generally a singleton/literal type like true or “hello” or 123 or even null or undefined. You can’t use another discriminated union as a discriminant … Read more
TS 4.1 You can use as clauses in mapped types to filter out properties in one go: type Methods<T> = { [P in keyof T as T[P] extends Function ? P : never]: T[P] }; type A_Methods = Methods<A>; // { render: () => void; } When the type specified in an as clause resolves … Read more
Yes this is possible. You can find all information here: https://www.typescriptlang.org/docs/handbook/declaration-files/templates/global-modifying-module-d-ts.html The important part is this: declare global { /*~ Here, declare things that go in the global namespace, or augment *~ existing declarations in the global namespace */ interface String { fancyFormat(opts: StringFormatOptions): string; } }
First of all, you need to install typings for Google Analytics in your devDependencies npm install –save-dev @types/google.analytics Then add your tracking code in the base index.html, and remove the last line as shown bellow: <body> <app-root>Loading…</app-root> <script> (function(i,s,o,g,r,a,m){i[‘GoogleAnalyticsObject’]=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,’script’,’https://www.google-analytics.com/analytics.js’,’ga’); ga(‘create’, ‘UA-XXXXXX-ID’, ‘auto’); // <- add the UA-ID // <- remove the … Read more
It’s very simple. Just install the definitions that you need via npm. For example if you need lodash you can do: npm install –save @types/lodash Once it’s installed you can use it right away in your project. Typescript will resolve the typings for the installed @types package from the node_modules/@types folder by default. There’s no … Read more