Encountering TypeScript error TS2339 while trying to utilize a method from a different class within an event handler and binding the current

My development setup includes a service called DomService for all DOM manipulation tasks.

Additionally, I have another service called ModalService that handles modal functionality.

Within the ModalService, there are some events being bound, with a method from DomService utilized as the listener. Here's an example:

document.body.addEventListener('focus', this.domService.keyPress.bind(this), true);

The keyPress function within DomService looks somewhat like this:

keyPress(event){
    if (event.which === key.escape) {
        event.preventDefault();
        this.hide();
    }
}

Although it functions correctly, TypeScript seems to see references to this as pointing to the DomService class instead of the ModalService class. As a result, TypeScript is flagging errors about the hide property not existing on type DomService.

Is there any way to resolve this issue and make TypeScript understand the context better?

Answer №1

If you want to modify the context of this within a function, you can achieve this by including it (along with its type) as the first argument of the function. For instance, if you wish to change the context of this inside the keyPress function to be a ModalService, you can do the following:

keyPress(this: ModalService, event) {
    if (event.which === key.escape) {
        event.preventDefault();
        this.hide(); // This will work now.
    }
}

To learn more about this feature, you can visit this link.

Furthermore, if the above solution is not satisfactory, you always have the option to add // @ts-ignore above any line causing an error to suppress it.

Answer №2

If you're looking to handle events in Angular, consider using the EventEmitter and subscribing to the "emit" event.

ModalService

this.subscriptionHide = this.modalService.getHideEmitter()
  .subscribe(() => this.hide());

DomService

hideEmitter: EventEmitter<any> = new EventEmitter();

keyPress(event){
    if (event.which === key.escape) {
        event.preventDefault();
        this.hideEmitter.emit(null);
    }
}

getHideEmitter() {
    return this.hideEmitter;
}

Answer №3

Consider updating your functions to arrow functions for better efficiency.

Replace

keyPress(event) {

With

keyPress = (event) => {

You can learn more about arrow functions in typescript here

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