Change the way detect nodejs environment

Can we use

  var isNodeEnv = function isNodeEnv() {
    return typeof global != 'undefined';
  };

instead of

  var isNodeEnv = function isNodeEnv() {
    return typeof window === 'undefined' || typeof document === 'undefined';
  };

To make angular universal works with some libraries, I’ve to provide a shim for window and document objects. If we use global object which is node-specific, we can address the issues better.

Thanks for the fantastic library.

[limonte]

Reopening the issue because unfortunately, I had to undo this change, see details in #1927

[zenflow]

Basically, I think the error “SweetAlert2 requires document to initialize” was correct in the first place. Just preventing that error from happening will not change the fact that “SweetAlert2 requires document to initialize”.