How to use values in HTML form in javascript function

Question

Hey Guys this is my first project so forgive me if this question is a bit basic. I'm trying to use information gathered from HTML forms to complete a javascript function and return the result to the user. The prompt comes back as NaN with a textbox. Why is my function failing?

I can't find anything specifically answering this question so any help would be great.

 <script> function avgHigh() { var open1 = document.getElementById("open1"); var high1 = document.getElementById("high1"); prompt(high1/open1) } </script> <table style="width:300px"> <tr> <td>Opening Rate 1: <input type="text" id="open1" value="22" /> </td> <td>High Rate 1: <input type="text" id="high1" value="33"> </td> <td>Low Rate 1: <input type="text" id="low1" value="323"> </td> <td>Close Rate 1: <input type="text" id="close1" value="234"> </td> </tr> <tr> <td>Opening Rate 2: <input type="Text" id="open2" value="345"> </td> <td>High Rate 2: <input type="text" id="high2" value="345"> </td> <td>Low Rate 2: <input type="text" id="low2" value="345"> </td> <td>Close Rate 2: <input type="text" id="close2" value="654"> </td> </tr> <tr> <td>Opening Rate 3: <input type="Text" id="open3" value="456"> </td> <td>High Rate 3: <input type="text" id="high3" value="456"> </td> <td>Low Rate 3: <input type="text" id="low3" value="83"> </td> <td>Close Rate 3: <input type="text" id="close3" value="75"> </td> </tr> <tr> <td>Opening Rate 4: <input type="Text" id="open4" value="3457"> </td> <td>High Rate 4: <input type="text" id="high4" value="357"> </td> <td>Low Rate 4: <input type="text" id="low4" value="357"> </td> <td>Close Rate 4: <input type="text" id="close4" value="0876"> </td> </tr> <tr> <td>Opening Rate 5: <input type="Text" id="open5" value="576"> </td> <td>High Rate 5: <input type="text" id="high5" value="456"> </td> <td>Low Rate 5: <input type="text" id="low5" value="6458"> </td> <td>Close Rate 5: <input type="text" id="close5" value="456"> </td> </tr> </table> <input type='button' onclick="avgHigh()" value='Growth on Day 1 (%)' /> 

Answer 1

Use value.

var open1 = document.getElementById("open1").value;
var high1 = document.getElementById("high1").value;
prompt(high1/open1)

Answer 2

You are trying to divide an HTMLInputElement by another HTMLInputElement, which doesn't make sense.

You need to get their values (with the .value property).