Question: Okay probbaly my question is very common, and so many aks this question and answer this. But i have (kinda) have another problem. Usually is work if i text it into vendor, text cgame will follow what i text on vendor (keyup on real time), and i can change it on cgname (not affect to text vendor). But this is my problem, when cgname is empty or i erase text i wanna instaly text cgname into text vendor i mean duplicat text vendor to cgname if text cgname is erase or empty. How do i did that?
this my code on jquery 

```
var cgname = $("#cgname");
        $("#vendor").keyup(function() {
                cgname.val( this.value );
        });

```

I'm really2 sorry if u dont understand me what i said, my english really2 worst. 

UPDATE :
So many people miss understanding my questio. So i'm gonna cleary.
1. I need duplictae text vendor into text cgname
2. If text cganme get erease or empty, go to point 1.

Answer: 
Based on AHJeebon's answer I think you are looking for this :

```js
$("#vendor").keyup(function() {
  $("#cgname").val( $(this).val());
});

$("#cgname").keyup(function() {
  var val = $(this).val();

  if(!val || val.length === 0 )
      $(this).val($('#vendor').val());
});
```

```html
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

CG Name <input id='cgname' type='text'>
Vendor  <input id='vendor' type='text'>
```
```html
<!doctype html>
<html>
 <head>  
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
  <style>
   div:not([class]){ color: red; }
  </style>
  <script>   
   $(document).on('keyup','#cgname',function() {
    vendor = $(this).val();
    console.log(vendor)
    $('#vendor').val( vendor );
   });   
  </script>
 </head>

 <body>
  <input id="cgname" type='text'>
  <input id="vendor" type='text'>
 </body>

</html>
```