Add takewhile() method to ElementArrayFinder

[alecxe]

The current fp toolset available on ElementArrayFinder is great, but, what if we continue to improve it?

For instance, recently I've needed a "take while" functionality which cannot be simply achieved with filter(). I needed to take elements until I hit a certain one - in my case it was a menu and I wanted to get all of the elements before a divider which had an empty text.

Currently, I've added the following to onPrepare():

protractor.ElementArrayFinder.prototype.takewhile = function(whileFn) {
    var self = this;
    var getWebElements = function() {
        return self.getWebElements().then(function(parentWebElements) {
            var list = [];
            parentWebElements.forEach(function(parentWebElement, index) {
                var elementFinder =
                    protractor.ElementFinder.fromWebElement_(self.ptor_, parentWebElement, self.locator_);

                list.push(whileFn(elementFinder, index));
            });
            return protractor.promise.all(list).then(function(resolvedList) {
                var filteredElementList = [];
                for (var index = 0; index < resolvedList.length; index++) {
                    if (!resolvedList[index]) {
                        break;
                    }
                    filteredElementList.push(parentWebElements[index])
                }
                return filteredElementList;
            });
        });
    };
    return new protractor.ElementArrayFinder(this.ptor_, getWebElements, this.locator_);
};

Example usage:

element.all(by.css("ul li a")).takewhile(function (elm) {
    return elm.getText().then(function (text) {
        return text;
    });
});

Would it make sense to make takewhile built-in? Thanks.

[sjelin]

I think this could actually be done with a filter:

protractor.ElementArrayFinder.prototype.takewhile = function(whileFn) {
  let failIndex = Infinity;
  return this.filter((elem, i) => {
    if (i >= failIndex) {
      return false;
    } else if (!whileFn(elem, i)) {
      failIndex = i;
      return false;
    } else {
      return true;
    }
  });
};