In the View File

 <script type="text/javascript">
      function fetch_comp(val){

        $.ajax({
          type:"POST",
          url:"<?php echo base_url()?>admin/admin_main/fetchData",
          data:{'c_name':val},
          datatype: "JSON",
          success: function(data){
            var obj = JSON.parse(data);
            $("#job_description").val(obj.job_description);
            $("#ctc").val(obj.ctc);
            $("#location").val(obj.location);
          }
        })
      }
</script>

In the Controller File

public function fetchData(){
    $val = $this->input->post('c_name');
    echo "<script>alert('$val');</script>";
}

The value is not being passed from the view page to controller page.