Protractor exemple

multiple-selector-using-each.js

/**
 * Get 2 level of selector using ".each" 
 */
return element
    .all(
        by.css('.selector')
    ) // return array of element
    .each(function(parentElement, rowIndex) {

        return parentElement
            .all(
                by.css('.sub-selector')
            )
            // ...

return-and-promise-everything.js

return element
    .all(
        by.css('selector')
    )
    .each(function(elem, index) {
        // ...
    }).then(function () {

        return element(by.css('selector')).click().then(function () {

            return element(by.css('selector')).click();
        })
    });