What's the difference between .closest() and .parents('selector')?

问题

What's the difference between these? Is one more efficient than the other? I'm a little bit confused to why they both exist. Say I have this markup:

<table>
    <tr>
        <td>...</td>
        <td><span class='toggle'>Toggle</span></td>
    </tr>
    <tr>
        <td>...</td>
        <td><span class='toggle'>Toggle</span></td>
    </tr>
    <tr>
        <td>..</td>
        <td><span class='toggle'>Toggle</span></td>
    </tr>
</table>

From the <span> tags I could use either $(this).closest('tr'); or $(this).parents('tr'); to access the parent/closest <tr> tag.

回答1:

parent returns the immediate parents (one for each element in the caller object) or nothing if the parent does not match the selector. closest returns the closest ancestor matching ancestor for each element (which can be the original element). The third similar function, parents, returns all matching ancestors (not including the element itself).

Generally, closest is more resistant to refactoring the HTML code than parent, if you choose the selector sensibly.

回答2:

(Note: The question was edited the day after being asked, changing the question from about parent to being about parents [note the plural]. Which kind of makes a difference!)

Re your original question about parent (singular) vs. closest: parent only ever goes one level up. closest starts with the current element (not just the parent) and keeps searching through ancestors until it finds a match (or runs out of ancestors).

Re your updated question about parents (plural) vs. closest: There are two differences:

Whether the current element is considered (it is with closest, it is not with parents).
Whether the search stops with the first match (it does with closest, it doesn't with parents).

From your original question:

From the tags I could use either $(this).closest('tr'); or $(this).parent('tr');

No, actually. $(this).parent('tr'); would return an empty jQuery object, because the parent of the span doesn't match the selector.

From your updated question:

From the tags I could use either $(this).closest('tr'); or $(this).parents('tr');

You could, provided that your tr isn't also within another tr (e.g., a table containing a table). If that's the case, you'll get the same result. But if you have a table within a table, with parents you'll get multiple trs (all of the ancestor tr elements).

Consider this structure:

<div class="wrapper">
  <div class="inner">
    <p>Testing <span>1 2 3</span></p>
  </div>
</div>

If we hook click on the span, this is what we get back from the three relevant methods:

$(this).parent('div') - Empty jQuery object, the parent of the span is not a div.
$(this).parents('div') - jQuery object with two divs in it, the "inner" and "wrapper" divs (in that order).
$(this).closest('div') - jQuery object with one div in it, the "inner" one.

Here's the result if we hook click on the span and use span as the selector:

$(this).parent('span') - Empty jQuery object, the parent of the span is not a span.
$(this).parents('span') - Empty jQuery object, the span has no ancestor spans.
$(this).closest('span') - jQuery object with the span that was clicked.

回答3:

.parent() only goes up one level, while closest() includes the current element, and all parents.

Example (selecting from the bottom div, x = matched elements):

             parent()  parent('body')   .closest('div')  .parents('div')
body     
   div                                                       x
      div       x        <nothing>                           x
this-->   div                                x

来源：https://stackoverflow.com/questions/8975985/whats-the-difference-between-closest-and-parentsselector

标签

jquery

dom-traversal