Question

Say,I have 5 paragraphs in the page.

if I execute:

p_array=$('p');
second_p=$('p:eq(1)');
$.inArray(second_p,p_array);

I get -1.
Any explanation?

Answer 1

Neither p_array nor second_p are arrays.

They are jQuery objects.

More specifically, p_array is a jQuery object containing a set of 5 DOM nodes. second_p is a jQuery object containing a set of 1 DOM node.

$.inArray can function on these jQuery sets of nodes, but you can’t compare a set against a set.

If you extract that one DOM node using the array subscript operator (jQueryObj[i]), then you’re no longer comparing a set against a set:

var p_array=$('p');
var second_p=$('p:eq(1)');
alert($.inArray(second_p[0], p_array)); // result: 1

See a live demo here.