codeigniter - dependent dropdown with jquery and ajax post

Question

view : learning_view.php

Here is the first dropdown which I am populating from database.

    <select name = 'category' id = 'category'>
        <option value="">-- Select Category --</option>
        <?php foreach($category as $item){ ?>
        <option value="<?php echo $item->id_cat; ?>"><?php echo $item->name; ?></option>
        <?php } ?>
    </select>
    <br><br>

What I want is to populate another dropdown which is dependent on the first dropdown. For that I have used the jQuery ajax post.

second dropdown:

    <select name = 'type' id = 'type'>
        <option value="">-- Select Type --</option>
        <?php foreach($type as $item){ ?>
        <option value="<?php echo $item->id_type; ?>"><?php echo $item->name; ?></option>
        <?php } ?>
    </select>
    <br><br>

ajax post:

    jQuery(document).ready(function(){
      $("#category").change(function() {
        var category_id = {"category_id" : $('#category').val()};
        console.log(category_id);

        $.ajax({
          type: "POST",
          data: category_id,
          url: "<?= base_url() ?>learning/dependent_dropdown",

          success: function(data){

            $.each(data, function(i, data){
            console.log(data.name);
            console.log(data.id_type)
            });
           }
         });
       });
     });

controller : learning.php

   public function dependent_dropdown()
   {
       if(isset($_POST['category_id']))
       {
           $this->output
           ->set_content_type("application/json")
           ->set_output(json_encode($this->learning_model->getType($_POST['category_id'])));
       }
   }

The data is coming from the database after ajax post which I checked by

    console.log(data.name);
    console.log(data.id_type)

in the console.

But couldn't able to figure out how to use the data in the second dropdown of my view.

I mean how can i populate the second dropdown with the data i have received after ajax post.

Answer 1

I found a solution to my problem by modifying the success function of the ajax post:

success: function(data) {
    $.each(data, function(i, data) {
        $('#type').append("<option value='" + data.id_type + "'>" + data.name + "</option>");
    });
}

Which append the value into the drop down.

<select name="type" id="type">
    <option value="">-- Select Type --</option>
</select>

I just gave the id of the select block into the success function of the ajax post and appended the value. It works but there is a problem which is when I change the selection of the first dropdown new value appears but the values which were showing for the previous selection doesn't go away.

Answer 2

Here is some modification of your answer

success: function(data)
{
    $('#type').html('<option value="">-- Select Type --</option>');

        $.each(data, function(i, data){
        $('#type').append("<option value='"+data.id_type+"'>"+data.name+"</option>");
        });
}

It will show only new items.