Dynamically adding option to the dropdown list instenly using text box | How to Show/Hide text box when select Other from dropdown list

JavaScript Code:

$(document).on('click','.btcl', function(){
    var dataString = 'Rule=comp_list';
    $.ajax({
        type: "POST",
        url: "ajax.php",
        data: dataString,
        cache: false,
        success: function(data){
            $("#company_list").html(data);
        }
    });
});
$(document).on('change','#enq_company', function(e){   
    var t=e.target.type;
    //var val = $('#enq_company option:selected').val();
    var val = $(this).val();
        if(val=="new" || t=="text") {
        var dataString = 'val='+val+'&Rule=ins_comp';
        $.ajax({
            type: "POST",
            url: "ajax.php",
            data: dataString,
            cache: false,
            success: function(data){
                $("#company_list").html(data);
            }
        });
    }
});

HTML Page:


<select name="enq_company" id="enq_company" style="width: 310px" required>
  <option value="">Select Company Name</option>
  <option value="1">Google</option>
  <option value="2">Yahoo</option>
  <option value="3">Amazon</option>
  <option value="4">Flipkart</option>
  <option value="new">Other</option>
</select>

PHP Code in Ajax File:

<?

if(!empty($_REQUEST['Rule']) && $_REQUEST['Rule']=="comp_list") {
?>
    <select name="enq_company" id="enq_company" style="width: 310px" required>
        <option value="">Select Company Name</option>
        <?php
            dropdown('hmp_companies', 'comp_id,comp_name', 'comp_status=1 order by comp_name', @$insid);
        ?>
        <option value="new">Other</option>
    </select>
<?   
} else if(!empty($_REQUEST['Rule']) && $_REQUEST['Rule']=="ins_comp") {
    $val=secure($_REQUEST['val']);
    if($_REQUEST['val']=='new' || empty($val)) {
?>   
    <input name="enq_company" id="enq_company" type="text" value="<? if(isset($_POST['enq_company'])) echo $_POST['enq_company']; else if(!empty($getid)) echo $row['enq_company'];?>" placeholder="Enter New Company Name" required>
    <a href="#x" class="icn-link-blue tooltip btcl" title="Back to Companies List"><i class="fa fa-refresh fa-lg" aria-hidden="true"></i></a>
<?   
    } else {
    // Insert   
    $results = get_data("hmp_companies","count(*) as cnt,comp_id","comp_name ='".$val."'");
    if($results[0]>0){
        $insid = $results[1];
    }else{
        $orderby=rns_max('hmp_companies','comp_order_by');
        $ins_rec['comp_order_by']= $orderby;       
        $ins_rec['comp_added_by']= $ERP_Uid;
        $ins_rec['comp_added_date']= $now_time;
        $ins_rec['comp_updated_date']= $now_time;
        $ins_rec['comp_name']=$val;
        $ins_rec['comp_description']=$val;
        $insid=insert_Defined('hmp_companies', array_map('trim',$ins_rec),1);
    }   
?>
    <select name="enq_company" id="enq_company" style="width: 310px" required>
    <option value="">Select Company Name</option>
        <?php
            dropdown('hmp_companies', 'comp_id,comp_name', 'comp_status=1 order by comp_name', @$insid);
        ?>
        <option value="new">Other</option>
    </select>
<?
    }
}?>