JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <select name='pro_name[]'>
    <option value='1'>Pro 1</option>
    <option value='2'>Pro 2</option>
    <option value='3'>Pro 3</option>
    </select>

    <input type='text' name='price[]'>
</div>
<div>
    <select name='pro_name[]'>
    <option value='1'>Pro 1</option>
    <option value='2'>Pro 2</option>
    <option value='3'>Pro 3</option>
    </select>

    <input type='text' name='price[]'>
</div>

JavaScript

var $last_select = null;
    $(document).ready(function(){
        $("select[name^=pro_name]").change(function(){
            $last_select = $(this);
            $('input[name^=price]', $last_select.parent()).val('something');
        });
    });