The filter function is used to filter qualified DOM elements from the wrapper set.

If we have an HTML file with the following content, get the < for the external class; A> Element, which you can easily do with a filter.

<a href="#" class="external">link</a>
<a href="#" class="external">link</a>
<a href="#">link</a>
<a href="#" class="external">link</a>
<a href="#" class="external">link</a>
<a href="#"></a>
<a href="#">link</a>
<a href="#">link</a>
<a href="#">link</a>
<a href="#">link</a>

Filter parameter types can be divided into two types:

1 pass the selector

Pass the filter function

If you use a selector as an argument, the usage is as follows

$('a').filter('.external')

Use anonymous filtering functions

$('a').filter(function(index) {
return $(this).hasClass('external');
})

The parameter index is the index of the result set.