I have three separate text boxes and want a button which copies all the content from the boxes into a 4th box. How can I do this with javascript?

```
<form>
<textarea cols="60" rows="5" id="box1">PAST: </textarea>
<br /><br />
<textarea cols="60" rows="5" id="box2">PRESENT: </textarea>
<br /><br />
<textarea cols="60" rows="5" id="box3">FUTURE: </textarea>

<br /><br />
<input name="" type="button" />
<br /><br />
<textarea cols="60" rows="5" id="box4">All Past Present Future</textarea>
</form>

```