k6: How to create a Selection from an Element

Question

Using Selection.each(fn) (see the k6 docs), the callback is passed an index and an Element. Element has a different API than Selection, and within the callback I’d like to use the Selection API on the passed Element so that I can operate on each Selection individually. In jQuery, I’d often do this:

$('li').each(function (index, element) {
  let container = $(element).closest('div.listContainer');
  // now do something with the `container`
});

I’ve tried inside the callback to do things like $(element) or Selection(element) but it errors saying those are undefined. (Kind of stabbing in the dark, since I don’t see in the docs how to do this.)

My code looks like:

mySelection.each((index, element) => {
  // here, I'd like to do element.closest('.someAncestorSelector') if element could be 'wrapped'
})

Is there a way in the jQuery-like Selection API in k6 to do this?

Answer 1

From the k6 docs on Selection.closest:

For each element in the set, get the first element that matches the selector by testing the element itself and traversing up through its ancestors in the DOM tree. [emphasis mine]

Which means that each is unnecessary and will be performed automatically (returning a new Selection instance with the closest elements).

const closestSelection = mySelection.closest('.someAncestorSelector');
closestSelection.each((index, closestElement) => {
  // now, do something with closestElement.
});

or as a single chain of expressions:

mySelection.closest('.someAncestorSelector')
  .each((index, closestElement) => {
    // now, do something with closestElement.
  });

---

Btw, even jQuery implicitly handles collections, so your jQuery code could be changed to:

const containers = $('li').closest('div.listContainer');
containers.each(function (index, container) {
  container = $(container);
  // now do something with the `container`
});