Question

I am trying get the previous element. So when click in the .percen I want to alert the value of the previous element. At the moment I get undefined. What is the problem?

<input class="c currency" type="text" name="artigoAlternativo1_C"/>
<input class="d currency percen" type="text" name="artigoAlternativo1_D"/>

<br/>

<input class="c currency" type="text" name="artigoAlternativo1_C"/>
<input class="d currency percen" type="text" name="artigoAlternativo1_D"/>

$.fn.percentageFormat = function () {
    this.each(function (i) {
        $(this).change(function (e) {
            var $curr = $(this);
            $curr_ = $curr.prev('.c');
            alert(this.value);
            alert($curr_.prev().value);
        });
    });
    return this;
}
$(function () {
    $('.percen').percentageFormat();
});

demo

Answer 1

You are calling the prev method twice and jQuery object has no value property, change:

alert($curr_.prev().value);

To:

alert($curr.prev().val());

or:

alert($curr_.val());

http://jsfiddle.net/2gf95/