angular reactive forms

/* Answer to: "" */

  Reactive forms are built around observable streams, where form
  inputs and values are provided as streams of input values, which
  can be accessed synchronously. Reactive forms also provide a
  straightforward path to testing because you are assured that
  your data is consistent and predictable when requested.
  For more information go to:
loginForm.get('username').valid && loginForm.get('username').touched