How to preventDefault() in HostListener Input action

问题

Im trying to write a directive that limit user to input numeric only characters in the input text control.

@Directive({
  selector: '[numericControl]'
})
export class NumericControlDirective {

    contructor(
        private el: ElementRef,
    ) {}

    @HostListener('input', ['$event'])
    onInput(e: any) {
        if (e.which < 48 || e.which > 57) {
            e.preventDefault();
        }
    }

}

Usage

<input type="text" placeholder="Volume" numericControl />

But it doesn't work, Anyone came across this issue?

回答1:

Use Keyboard event type - keydown or keypress:

@HostListener('keydown', ['$event'])
onInput(e: any) {
  if (e.which < 48 || e.which > 57) {
      e.preventDefault();
  }
}

回答2:

You can also use

@HostListener('keydown', ['$event']) onKeyDown(event) {
    let e = <KeyboardEvent>event;
    if (e.which < 48 || e.which > 57) {
        e.preventDefault();
    }
}

来源：https://stackoverflow.com/questions/50022255/how-to-preventdefault-in-hostlistener-input-action