ngLimitCharectersOnInput.ts

    public only($event: KeyboardEvent) {
        console.log("press");
        let regex: RegExp = new RegExp(/^[0-9a-zA-Z]{1,}$/g);
        let specialKeys: Array<string> = ['Backspace', 'Tab', 'End', 'Home', 'ArrowRight','ArrowLeft'];
        if (specialKeys.indexOf($event.key) !== -1) {
        return;
        } else {
        if (regex.test($event.key)) {
            return true;
        } else {
            $event.preventDefault();
            return false;
        }
        }
    }
    
    //    <input type="text" (keypress)="only($event)" />