如何在HTML中为价格添加自动点？

I'm trying to implement automatic formatting to an web-page. So that when you type 12345678, it is automatically €123.456,78.

      <div class="form-group">
<input type="text" required class="form-control" name="EKBrutto" placeholder="EK-Brutto">

I have no clue how to do this.

You can use the following link to mask money, Especially you are dealing with money

https://plugins.jquery.com/maskMoney/

And this following link is a demo

http://plentz.github.io/jquery-maskmoney/

basically what you have is:

<input type="text" id="currency" />

then you put in this script

<script>
  $(function() {
    $('#currency').maskMoney();
  })
</script>

This automatically puts the dots in place, but there are more parameters to help you just read the guide :)