Reusable functions for Protractor test framework - testing

Question

I use Protractor Test Framework and need to use some the same operations for different cases. Like Authentication procedure.
The question is: What's the correct way to use own functions in Protractor?
I remember this tool works: 1) asynchronous and 2) its functions return promises.
Must the reusable function return the promise for make possibility do .then() operation or this function may return no value?
An Example (correct or no):
describe('Login procedure', function() {
it('Login Username', function () {
browser.get('anurl.com');
auth('username', 'password').then(function(){console.log('NICE TO MEET YOU')});
});
var auth = function(loginstr, passwordstr) {
return element(by.css('div[class="login"]')).isDisplayed().then(function (result) {
if (result) {
element(by.css('input[name="email"]')).clear().sendKeys(loginstr).then(
function () {
element(by.css('input[name="password"]')).clear().sendKeys(passwordstr).then(function () {
element(by.css('button[class="submit"]')).click().then(function () {
return element(by.id('welcome')).isPresent();
});
});
});
}
});
}
Thanks!

Answer 1

Your example looks fine.
It is good practice to return a promise from your utility functions (so callers can then off of it if they want). But it is not required.
In practice, the methods you are invoking that create promises (e.g., click or isDisplayed, etc) implicitly register the created promise with the control flow, so the implicit synchronization will not be impacted by refactoring the calls into your own functions.
See the Protractor Page Objects for a similar approach.

Answer 2

Our team uses Orchid-js with Jasmine and Protractor.
It's an extension that makes defining your own functions automatic.
In this case your code will still work, you would just be able to automatically reuse your 'Login procedure' and 'Login Username' functions as well.
Describe('Login procedure', function(username,password) {
It('Login Username', function (username,password) {
browser.get('anurl.com');
auth(username, password).then(function(){console.log('NICE TO MEET YOU')});
})(username,password);
})('username','password');
Then reuse it later
Describe('Login procedure')('differentUsername','differentPassword');