I'd like to prevent the user from clicking the button "Register" if the fields are not correct. Part of that is that certain fields must be filled. But the condition is starting to get a bit long:
<button class="btn btn-success" ng-click="register()"
ng-disabled="signInForm.$invalid || form.firstName.length==0 ||
form.lastName.length==0 || form.email.length==0 ||
form.password.length==0 || form.passwordBis.length==0">Register</button>
How can I simplify that?