Angular2将编译器错误引发给在subscribe（）中运行的内容

Question

I have a textarea on which I want to listen to keyup events. Everything works fine except that Angular2 throws an error compile-time (not runtime).

The error:

error TS2339: Property 'target' does not exist on type '{}'.

The code:

Observable.fromEvent(this.editor.nativeElement, 'keyup')
          .debounceTime(500)
          .subscribe(event => this.hasError = !this.isValidJSON(event.target.value));

Obviously the error is suggesting that event is an empty object.

As I said, the keyup event and my application runs fine but this error is annoying and I want to get rid of it. How can it complain about event being an empty object during compile-time ? It has never even been run, and during run-time everything works.

Answer 1

You need to cast to the appropriate type:

I suggest you cast to KeyboardEvent (which inherits from ES6's Event ) or, if you just want to get rid of the error use any :

subscribe((event: KeyboardEvent) => ...);

or

subscribe((event: any) => ...);

If you just use Event there might be a mixup with Event automatically imported from @angular/router .

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