Learning how to implement the "as" syntax in TypeScript

Question

Learning how to implement the "as" syntax in TypeScript

Currently tackling an angular project that is functioning flawlessly, yet encountering a linting test failure. Unfortunately, the information provided in this post did not offer much assistance. The error message I'm facing reads as follows:

ERROR: C:/Users/.../monthpicker.component.ts:164:22 - Type assertion using the '<>' syntax is forbidden. Use the 'as' syntax instead.
Lint errors found in the listed files.

The problematic code on line 164 within my ts file appears like so:

testMethod() {
    this.text = (<HTMLInputElement>document.getElementById('rangeInput')).value;
}

Still fairly new to Angular, I am unsure of the appropriate steps to rectify this issue. Removing the <> characters proves challenging as the rangeInput element is integral to my HTML structure:

<input id="rangeInput" [ngModel]="text" placeholder="Select range" />

Your guidance is highly appreciated in resolving this matter and successfully passing the linting test. Currently utilizing Node v10.15.3.

PS: It's worth noting that no errors or warnings occur during regular project operation; the linting tests only surface upon initiating a git push.

angular typescript

Answer 1

Answer №1

While I have not personally tried this out, typically the correct syntax is as follows:

testMethod() {
    this.text = (document.getElementById('rangeInput') as HTMLInputElement).value;
}

You can give it a try and see if it works for you.

Answer 2

While I have not personally tried this out, typically the correct syntax is as follows:

testMethod() {
    this.text = (document.getElementById('rangeInput') as HTMLInputElement).value;
}

You can give it a try and see if it works for you.

Answer 3

Answer №2

// When working independently

// Add before the statement
// -/ <desiredType>ResolveStatement();
const canvas1 = <HTMLCanvasElement>document.getElementById("something");
// Add after the statement
// -/ ResolveStatement() as desiredType;
const canvas2 = document.getElementById("something") as HTMLCanvasElement;

// Use parentheses when grouping is needed

// Add before the statement
// -/ <desiredType>ResolveStatement();
const canvasHasWidth1 = (<HTMLCanvasElement>document.getElementById("something")).hasAttribute("width");
// Add after the statement
// -/ ResolveStatement() as desiredType;
const canvasHasWidth2 = (document.getElementById("something") as HTMLCanvasElement).hasAttribute("width");

To improve clarity, consider adopting a consistent casting method by following linting rules.

Answer 4

// When working independently

// Add before the statement
// -/ <desiredType>ResolveStatement();
const canvas1 = <HTMLCanvasElement>document.getElementById("something");
// Add after the statement
// -/ ResolveStatement() as desiredType;
const canvas2 = document.getElementById("something") as HTMLCanvasElement;

// Use parentheses when grouping is needed

// Add before the statement
// -/ <desiredType>ResolveStatement();
const canvasHasWidth1 = (<HTMLCanvasElement>document.getElementById("something")).hasAttribute("width");
// Add after the statement
// -/ ResolveStatement() as desiredType;
const canvasHasWidth2 = (document.getElementById("something") as HTMLCanvasElement).hasAttribute("width");

To improve clarity, consider adopting a consistent casting method by following linting rules.

Answer 5

Answer №3

It's possible that you don't even need the "as" keyword. Have you attempted the following:

testMethod() {
    this.text = (document.getElementById('rangeInput')).value;
}

You can also refer to an example here

const el: HTMLElement = document.getElementById('content');

If all you require is passing a value to the method, you can simply use

<input id="rangeInput" [ngModel]="text" placeholder="Select range" (change)="testMethod($event)" />

testMethod(event: any) {
    this.text = event.target.value;
}

Note that you have the flexibility to utilize any other event supported by input elements to trigger the method (besides change as demonstrated here)

An alternative approach would be to implement two-way binding as outlined here

<input id="rangeInput" [(ngModel)]="text" placeholder="Select range"/>

const text: string;

Answer 6

It's possible that you don't even need the "as" keyword. Have you attempted the following:

testMethod() {
    this.text = (document.getElementById('rangeInput')).value;
}

You can also refer to an example here

const el: HTMLElement = document.getElementById('content');

If all you require is passing a value to the method, you can simply use

<input id="rangeInput" [ngModel]="text" placeholder="Select range" (change)="testMethod($event)" />

testMethod(event: any) {
    this.text = event.target.value;
}

Note that you have the flexibility to utilize any other event supported by input elements to trigger the method (besides change as demonstrated here)

An alternative approach would be to implement two-way binding as outlined here

<input id="rangeInput" [(ngModel)]="text" placeholder="Select range"/>

const text: string;

Answer 7

Answer №4

I highly recommend removing the use of document.getElementById from your code as it may cause complications as your project grows more intricate, especially since it functions outside of Angular.

If you need to access the rangeInput, simply pass it to your function after assigning it an Angular id:

<input id="rangeInput" #angularIdExample [ngModel]="text" placeholder="Select range" />

Then, send it to your method using a button like this:

<button (click)="testMethod(angularIdExample)">testMethod</button>

Now, in your method, ensure you specify the correct type when accessing it:

testMethod(inputElement: HTMLInputElement) {
    this.text = inputElement.value;
  }

For a working example, check out: https://stackblitz.com/edit/angular-sending-input-reference

Answer 8

I highly recommend removing the use of document.getElementById from your code as it may cause complications as your project grows more intricate, especially since it functions outside of Angular.

If you need to access the rangeInput, simply pass it to your function after assigning it an Angular id:

<input id="rangeInput" #angularIdExample [ngModel]="text" placeholder="Select range" />

Then, send it to your method using a button like this:

<button (click)="testMethod(angularIdExample)">testMethod</button>

Now, in your method, ensure you specify the correct type when accessing it:

testMethod(inputElement: HTMLInputElement) {
    this.text = inputElement.value;
  }

For a working example, check out: https://stackblitz.com/edit/angular-sending-input-reference

Learning how to implement the "as" syntax in TypeScript

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

How can we fetch data from the server in Vue 2.0 before the component is actually mounted?

"Linking a Next.js application with Azure's Application Insights for advanced insights

Angular: Unable to locate route declaration in the specified path /src/app/app-routing.module.ts

Let's grab the hang on pipeline server by running `npm install

Using React and TypeScript to Consume Context with Higher Order Components (HOC)

Access network path through browser using Angular

After inputting new values, the table is not allowing me to update it

What is the best way to ensure all keys of a certain type are mandatory, while still allowing for the possibility of

What is the process of personalizing a DaisyUI theme in Tailwind with TypeScript?

When using Angular and opening a portal in a separate window, what is the best way to connect an overlayRef in order for it to utilize the component's unique styles?

How can we transfer or exclude all boolean properties from one class to another or a "type"?

Suggestions for developing a component library for angular/react modules

Leverage properties within the storybook component template

I am having trouble with a property that I believe should be recognized but is not

Variety of type 'class' in Typescript

Receiving information from the Angular server located at IP address 127.0.0.1

Issues with Angular Material animations may arise following the implementation of a custom theme

Transmit information through a router connection

Here's how to update an inaccurate TypeScript type definition that was installed through @types/package

The switchMap function is sending back a single item