Combining result (ORing) of 2 validators in Angular and using it as single validating factor

I want to get a validation result on a form field by ORing the 2 validation results

e.g.

this.registerForm = this.formBuilder.group({
username: ['', [Validators.required,Validators.pattern(USERNAME_REGEX) || Validators.email]],
});



Is something like this possible?

Constraints: THE USERNAME SHOULD BE EITHER AN EMAIL ADDRESS OR SHOULD BE A VALID USERNAME WHICH MATCHES TO THE PATTERN OF USERNAME'S REGEX

I want to use angular's inbuilt email validators' output and the output of a custom made regex pattern to identify whether the field is valid or not.

PS: I have refered this post -> Angular 2 combined form validation but it does not match my condition

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