Change object properties dynamically to meet requirements in TypeScript

Question

Change object properties dynamically to meet requirements in TypeScript

Let's say I have a function that outputs the following:

interface result {
  A?: string;
  B?: string;
  C?: string;
}

When using an array parameter in a function, how can I make certain return parameters non-nullable and required? For example:

function toRequired(keysToTurnRequired: string[]): CorrectResult {
}

If I were to execute toRequired(['A', 'B']), then my return type should be updated to this:

result {
  A!: string;
  B!: string;
  C?: string;
}

Is there a generic method in Typescript to achieve this easily? This would greatly enhance type safety when working with ORM repositories.

typescript

Answer 1

Answer №1

It is possible to define types in advance and then apply type narrowing, but the creation of types during runtime is not feasible in TypeScript. This is because TypeScript primarily serves as a tool for developers in the development environment, and by the time the code runs, it has already been converted into JavaScript.

interface ResultBase {
    A?: string;
    B?: string;
    C?: string;
  } 
  
  interface ResultAB extends Partial<ResultBase> {
    A: string;
    B: string;
  }

  const isResultAB = (candidate: ResultBase): candidate is ResultAB => {
      return ('A' in candidate && typeof 'A' === 'string') &&
         ('B' in candidate && typeof 'B' === 'string')
  }

  const x = {
      A: 'sfsdf',
      B: 'bbbb'
  }

  if (isResultAB) {
      // Now we know we have a type ResultAB
  }

Answer 2

It is possible to define types in advance and then apply type narrowing, but the creation of types during runtime is not feasible in TypeScript. This is because TypeScript primarily serves as a tool for developers in the development environment, and by the time the code runs, it has already been converted into JavaScript.

interface ResultBase {
    A?: string;
    B?: string;
    C?: string;
  } 
  
  interface ResultAB extends Partial<ResultBase> {
    A: string;
    B: string;
  }

  const isResultAB = (candidate: ResultBase): candidate is ResultAB => {
      return ('A' in candidate && typeof 'A' === 'string') &&
         ('B' in candidate && typeof 'B' === 'string')
  }

  const x = {
      A: 'sfsdf',
      B: 'bbbb'
  }

  if (isResultAB) {
      // Now we know we have a type ResultAB
  }

Change object properties dynamically to meet requirements in TypeScript

Answer №1

Similar questions

Executing an asynchronous function within an Angular 7 interceptor is crucial

What is the best way to launch an event when a component is accessed through navigation?

Relaying numerous references in TypeScript

Tips for aligning the arrow of a dropdown menu option

VueJS - When using common functions, the reference to "this" may be undefined

Typescript has a knack for uncovering non-existent errors

Is it possible to regulate the type of a class that has not yet been instantiated?

Fetching data in VueJs before redirecting to a new page

Issue with Angular2 where stylesheets are not loading properly

Invoke the subscribe function within the encompassing parent function

Is it possible to use Eclipse for debugging AngularJS and TypeScript code?

Tips for transferring information between two components when a button is clicked in Angular 2

Execute child function in Angular after parent completes operations on observables within a forEach loop

Tips for initializing and updating a string array using the useState hook in TypeScript:1. Begin by importing the useState hook from the

Attempting to build a table within a table structure

Deleting and inserting an element in the Document Object Model

What is the process for creating a method within a class?

Having trouble reading the length property of undefined in Angular 7

Ways to confirm non-null values and bypass the row if it is

The guard check may not be enough to prevent the object from being null