Angular 2 Multiple validators

You can combine validators using Validators.compose()

this.username = new Control('', 
    Validators.compose(
        [Validators.minLength(5), Validators.required]));

for async validators use

this.username = new Control('', null,
    Validators.composeAsync(
        [someAsyncValidator, otherAsyncValidator]));

There are open issues with async validators, especially sync validators combined with async validators don’t work

• https://github.com/angular/angular/issues/8923
• https://github.com/angular/angular/issues/1068

To make sync validators work with async validators, wrap the sync validators in promises and compose them as async valdiators like

this.username = new Control('', null,
    Validators.composeAsync([
        (control:Control) => Promise.resolve(Validators.minLength(5)(control)), 
        (control:Control) => Promise.resolve(Validators.required(control)),
        someAsyncValidator, otherAsyncValidator
    ]));