Select nth child in jquery javascript

Question

select nth child like this I want to select seconds child .

$(this).prev().children[1].removeClass("necry").addClass("necry_er");

And this HTML

<div class="reg_label">
    <div class="def">Family</div>
    <div class="necry">Necessary Field</div>
    <div class="clear">&nbsp;</div>
</div>

I expect this result:

<div class="necry_er">Necessary Field</div>

Answer 1

what about something like this?

var nec = $(this).parent().find(".necry");
nec.removeClass("necry");
nec.addClass("necry_er");

Answer 2

Use eq() to reduce a set of matched elements to the one at the specified index.

$(this).prev().children().eq(1).removeClass("necry").addClass("necry_er");

There's also a :nth-child selector:

$('#elementID:nth-child(2)').doSomething();

To just swap the two classes you can do:

$('.necry').toggleClass('necry necry_er');

How exactly to go about finding the element you want is a little hard to tell, as there is no explanation as to what this is or what context it is in ?