Looking to derive the numerical length of a string:
type Length = LengthOfString<"hello">
// ^? should equal 5
Feeling a bit lost on how to approach this. Any guidance on how to achieve this?
(Currently diving into typescript's type system for learning purposes -- not intended for JS code)
In order to separate each character of a string, one approach is to utilize a template literal string. This method involves adding an element to the tuple L for every character that can be extracted from the string.
type LengthOfString<T extends string, L extends any[] = []> =
T extends `${string}${infer R}`
? LengthOfString<R, [...L, string]>
: L["length"]
Once all characters have been processed, the function returns the length of L.
Outcome:
type Length = LengthOfString<"hello">
// ^? 5
I am looking to implement a file existence check on every page of my app. The idea is that if a specific file exists, the user should be redirected to another page. One solution I have considered is using a Higher Order Component (HOC) for this purpose. A ...
TS Playground of the problem function callStringFunction(callback: (s: string) => void) { callback("unknown string inputted by user"); } function callNumberFunction(callback: (n: number) => void) { callback(4); // unknown number inputt ...
Struggling to find a smart way to share code between two interconnected projects? Look no further! I've got a React web app encompassing client code and an Express app serving as both the API and the React web app host. Since I use Typescript in both ...
I've been encountering this issue where I keep getting an error message. I attempted to resolve it by setting "noImplicitAny": false in tsconfig.json, but unfortunately that did not work. As for the 'Property does not exist on type' error, I ...
Here is a snippet of my code: async run(minutesToRun: number): Promise<void> { await authenticate(); await this.stock.fillArray(); await subscribeToInstrument(this, this.orderBookId); await subscribeToOrderbook(this, this.orderBookId ...
When it comes to Svelte, the final output is native JavaScript classes, which TypeScript can understand. However, before TypeScript can recognize Svelte components, they must first be compiled from their initial .html form. This can lead to a 'cannot ...
Consider the following function: type User = { id: string, name: string } interface Props { user: User; } export const getUserInfo: GetUserInfo<User> = async ({ user }: Props) => { const userData = await fetchUser(user.id); return ...
How can I trigger a type error in TypeScript 4.4.3 for the incorrect string 'c' below, which is not one of the keys of the object that is passed as the first parameter to the doSomething method? const doSomething = ({ a, b }: { a: number, b: stri ...
I have a React + TypeScript application with server-side rendering (SSR). I am using Material-UI and following the SSR instructions provided here. Most of my components are stateful, and I test them using Jest + Enzyme. Below is an example of one such com ...
My text editor is not displaying correctly on my website. Please refer to the following images for reference: Top of the page Bottom of the page Currently, it only shows a large SVG and a few input fields at the bottom. The technologies I am using includ ...
Is there a way to convert a base64 string image to a blob image in order to send it to the backend using a form? I've tried some solutions like this one, but they didn't work for me. function b64toBlob(b64Data, contentType='', sliceSiz ...
Requesting assistance to develop a webapp using Angular4 with THREEjs for viewing Collada Objects, but encountering challenges. UPDATE: Seeking a working example or helpful hints as efforts in researching and exploring code with other loaders have prove ...
I would like to utilize the getByRole function for writing my test. However, I am encountering issues when using linkitem or 'link' as the role. It seems that I cannot find the desired element. // encountered error TestingLibraryElementError: The ...
We encountered an error while attempting to embed a report using the Power BI Angular library. TypeError: Cannot read properties of undefined (reading 'tokenType') at isSaaSEmbedWithAADToken (reportEmbed?navContentPaneEnabled=false&uid=am ...
I'm facing a challenge where I have various styled components with some shared styles. To address this, I decided to create a function that takes in a `theme` parameter and outputs the common styles being used. Here's a glimpse of what I came up ...
I'm diving into my initial TypeScript project and encountering an issue with the "style". I attempted to utilize style!, create an if(changeBackgroundColor){}, but without success. let changeBackgroundColor = document.querySelectorAll('[data-styl ...
In my definitions, I have identified two distinct groups: Tabs and Sections. A section is encompassed by tabs (tabs contain sections). When defining sections, I want the tab names to be automatically populated by the previously declared sibling tabs. But ...
I am attempting to develop a feature in Angular 9 that takes user input from a textarea, processes it, and then presents it back to the user as a downloadable (txt) file. The structure of the form in app.component.html is as follows: <form (ngSubmit)= ...
Currently, I am working on a VueJS project that utilizes ViteJS for transpilation, which is functioning properly. However, when Jest testing is involved alongside ts-jest, the following Jest configuration is used: jest.config.ts import { resolve } from &q ...
Why is the somma value showing the concatenation of totaleEnergetico and totaleStrutturale instead of a sum? RiepilogoCombinatoStComponent.ts export class RiepilogoCombinatoStComponent implements OnInit { constructor() { } interventi: AssociazioneI ...