Question

I have table rows like so:

<tr class="parent0 row3" data-parent="0">
   <td>...</td>
</tr>
<tr class="parent3 row7" data-parent="3">
   <td>...</td>
</tr>
<tr class="parent3 row12" data-parent="3">
   <td>...</td>
</tr>
<tr class="parent0 row8" data-parent="0">
   <td>...</td>
</tr>
<tr class="parent0 row9" data-parent="0">
   <td>...</td>
</tr>

So if I have a click handler:

$(document).on({
   "click": function(){
      var parentId = $(this).data("parent");
      //get previous sibling:
      //OPTION A:
      var prevParentA = 
              $(this).prev("parent" + parentId); //works sometimes
      //OPTION B:
      var prevParentB = 
              $(this).prevAll("parent" + parentId).eq(0); //works all the time but ugly...
   }

}, "tr");

Option A only works when the direct previous item has the same parent, but when that is not the case, prevParentA === [] which is not the desired result.
Option B always seems to work, but it is ugly in that it is selecting ALL of the previous items matching that class and selecting the 1st one it finds.

Is there a better option than Option B?

Answer 1

jQuery does not have something better than your option B. I’ve long thought this was a missing piece of functionality as I’ve regularly wanted something like it too. Fortunately, it’s not too hard to make your own method:

jQuery.fn.prevFind = function(selector) {
    var elems = [];
    this.each(function(i, item) {
        while (item = item.previousSibling) {
            if (item.nodeType == 1) {
                if ($(item).is(selector)) {
                    elems.push(item);
                    break;
                }
            }
        }
    });
    return(this.pushStack(elems, "prevFind", selector));
}

The same could be done for a nextFind() also.

In your example, instead of this:

$(this).prevAll("parent" + parentId).eq(0);

you would use this:

$(this).prevFind("parent" + parentId)

---

And, here’s an implementation of both prevFind() and nextFind() that uses some common code:

(function($) {

    $.each({
        'prevFind' : 'previousSibling',
        'nextFind' : 'nextSibling'
    }, function(method, dir) {

        $.fn[method] = function (selector) {

            var elems = [];

            this.each(function(i, item) {
                while (item = item[dir]) {
                    if (item.nodeType == 1) {
                        if ( $.find.matches(selector, [item]).length ) {
                            elems.push(item);
                            break;
                        }
                    }
                }
            });

            return this.pushStack(elems, method, selector);
        };
    });

}(jQuery));

Here’s the fiddle: http://jsfiddle.net/nDYDL/1/