Protractor:count() doesn't work outside of expect()

I tried to write a function to wait for the number of some kinds of elements to be a specific number, my code is:

waitelementnum= function (num) {
    var elmnum=element.all(by.xpath("//div[@class='notification-content']")).count();
    browser.wait(function () {
        return (elmnum>num);
    }, 10000);
};

but it always timeout. then I try to print the result of count like:

console.log(element.all(by.xpath("//div[@class='notification-content']")).count());

nothing was printed out;

but when I tried:

expect(element.all(by.xpath("//div[@class='notification-content']")).count()).toEqual(2);

it reported:

expecting 1 to be 2.

So world anybody kindly tell me what's wrong with my function?