Use element by css to check if element exists in Protractor

You need to test if the element is not present:

expect(element(by.css('.elementClass')).isPresent()).toBe(false);

You can test whether the element is present with isPresent. Here are the protractor docs for the isPresent function.

So, your code would be something like:

var myElement = element(by.css('.elementClass'));
expect(myElement.isPresent()).toBeFalsy();