Populate text field based on drop down

[Alessaa]

 I've got a drop down menu that is called Ressourcen and a single text field that is called Zusatztext3. Now I would like to insert every selection that is made in the drop down, into my text field. But everytime I select a element in the drop down menu, it appears twice in the text field. How can I fix that, I want it to appear only once.
My current Javascript:

for(var i=1;i<10;i++){
 if(this.getField("Ressourcen".value == i){
  this.getField("Zusatztext3").value += event.value;

  this.getField("Zusatztext3").value += ",";

}}

[Bernd Alheit · Accepted solution]

As validation script use:

this.getField("Zusatztext3").value += event.value + ",";

[Bernd Alheit]

Where does you use this wrong script?

[Alessaa]

I've created a Adobe Acrobat DC pro PDF form and I inserted the script into the JavaScript option (in the tab format) in the drop down menu "Ressourcen"

[Bernd Alheit]

Why does you use the for loop?

[Alessaa]

Because I want to insert every selection from the drop down menu into the text field. For example if I click on the item apple and after that I click on the item banana in the drop down Menu, then I want it the be displayed as: apple, banana in the text field. But my problem is that it is being displayed as apple, apple, banana, banana right now.

[Bernd Alheit · Accepted solution]

As validation script use:

this.getField("Zusatztext3").value += event.value + ",";

[Alessaa]

I run into the same problem with this script. The selected element appears multiple times in the text field. But I only selected it once.

[Bernd Alheit]

Can you share the form?

[Alessaa]

I added the form to my post.

[try67 · Accepted solution]

You added the script to the wrong location. It needs to be a Validation script, not a Format script.

[Alessaa]

Thank you! It works now