Problem With Variables And Objects

Question

I have 3 TextFields, called txtUSD, txtEUR, txtAUS. And a PopupList with the same values, minus the txt part, but I need to form the names of the TextFields to use based on the selection that the user made. So I've done this:

function btConvert_Click(event)
{
    var amount = document.getElementById("txtAmount").value;
    var rates = document.getElementById("lstConvertTo").value;
    var from = "txt" + document.getElementById("lstFrom").options[document.getElementById('lstFrom').selectedIndex].text;
    var to = "txt" + document.getElementById("lstConvertTo").options[document.getElementById("lstConvertTo").selectedIndex].text;
    var curr_from = document.getElementById(from).value;
    var curr_to = document.getElementById(to).value;

    if(curr_from > curr_to)
    {
        amount * rates;
    } else {
        amount / rates;
    }
    alert(result);
}

But every time I try it I get this error:

mobile/main.js line 215: Result of expression 'document.getElementById(from)' [null] is not an object.

How should I make it?

They are all at value and the values of from and to should be the combination of txt + The selected value — Nathan Campos
– Nathan Campos, Commented Apr 3, 2011 at 13:02

Nathan Campos · Accepted Answer · 2011-04-04 21:00:17Z

1

From the error you're getting, it looks like there's a bug when generating the from variable.

You should consider storing document.getElementById('lstFrom') into it's own var, for brevity.

edited Apr 4, 2011 at 21:00

Nathan Campos

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answered Apr 3, 2011 at 2:11

scribu

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