how to get the value of an control

 If a html page contains what likes:

<table>
        <tr>
            <td>
                Enter Key Here ->
                <input type="text" id="key" name="key"
                       onkeyup="convertToDecimal( );">

            </td>
        </tr>
    </table>
    <br />
    <table>
        <tr>
            <td colspan="5" style="border-bottom:solid black 1px;">
                Key Pressed:
                <input type="text" readonly id="keypressed">
            </td>
        </tr>
      </tabl

We can get keys using getElementById( keyId ),

var key = document.getElementById("key");

var keypressed = document.getElementById("keypressed");

And we can put the value of key into the value of keypressed like this:

keypressed.value = key.value;

So we can get the value of a <input> control by:

myvalue = document.getElementById("keyId").value;