I am attempting to create a couple of web pages that will allow me to fill out a form on `input.html` and have the entered data appended to a different HTML file, `index.html`.

I have been searching for an answer for a couple of hours now and it might just drive me insane!

Here is some example code of what I'm trying to do:

* HTML form `input.hmtl`:

```
<form>
   <label>
      Enter something:
      <input type="text" id="userinput" required>
   </label>
   <input type="submit" id="submit" value="submitted">
</form>

```

* Javascript to get entered data and pass to `index.html`:

```
var userInput = document.querySelector("#userinput");
var submit = document.querySelector("#submit");

function addToIndex() 
{
   // create new element on index.html
}

submit.addEventListener("click", addToIndex, false);

```

* HTML output file `index.html`:

```
<div id="contentstart">
   <!-- newly created element here -->
</div>

```

I have attempted using [this](https://stackoverflow.com/a/10240754/11737012) solution, but Chrome's console gives me an error and tells me that `newWindow is not a function`. I just stumbled upon using the `<iframe>` element in a couple of answers but don't quite understand it yet (I'm a noob).

Thanks in advance!