Get Java Variable to Reference Form Input

Question

I am trying to get the document.bmi.answer.value to equal to ans. But it is not showing up. Does anyone see any errors in my code?

This is in my head:

<script type="text/javascript">
function calcbmi()
{
var hh = parseFloat(document.getElementByName('height').value);
var ww = parseFloat(document.getElementByName('weight').value);
var ans = (( ww / ( hh * hh ))*703);
document.getElementByName('answer').value = ans;
}
</script>

This is in my body:

<form name="bmi">
<p> Height <input type="text" name="height"></p>
<p> Weight <input type="text" name="weight"></p>
<p> BMI <input type="text" name="answer" value=""></p>
<input type="button" value="Calculate" onclick="calcbmi();">
</form>

Thanks for the help!

Here is my whole code as my error my not reside in the javascript or form. I cant for the life of me see it though..

<!DOCTYPE HTML>
<html>
<head>
    <title></title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript">
function calcbmi()
{
var hh = parseFloat(document.getElementByName('height').value);
var ww = parseFloat(document.getElementByName('weight').value);
var ans = (( ww / ( hh * hh ))*703);
document.getElementByName('answer').value = ans;
}
</script>
</head>
<body>
<h1>Body Mass Index</h1>
<form name="bmi">
<p> Height <input type="text" name="height"></p>
<p> Weight <input type="text" name="weight"></p>
<p> BMI <input type="text" name="answer" value=""></p>
<input type="button" value="Calculate" onclick="calcbmi();">
</form>
</body>
</html>

What you're talking about is JavaScript, not Java the server-side programming language. — adarshr
– adarshr, Commented Apr 17, 2013 at 16:51
Looks like you have an extra ) at the end of var ans = ( ww / ( hh * hh ))*703); — Jason Sperske
– Jason Sperske, Commented Apr 17, 2013 at 16:56
Thanks! I fixed it but it still has not solved my over all problem of my answer not showing up in the BMI box. — user2291730
– user2291730, Commented Apr 17, 2013 at 17:00
Now your fix has introduced a new bug (I've addressed this in my answer) — Jason Sperske
– Jason Sperske, Commented Apr 17, 2013 at 17:06

Jason Sperske · Accepted Answer · 2013-04-17 17:05:28Z

1

There is a bug in your JavaScript that is preventing it from executing (here is a demo)

function calcbmi() {
    var hh = parseFloat(document.bmi.height.value);
    var ww = parseFloat(document.bmi.weight.value);
    var ans = (ww / (hh * hh)) * 703;
    document.bmi.answer.value = ans;
}

Remove the extra ) and you should be good

Now that you've updated your code to fix the parenthesis you have introduced a new bug, the command you want (assuming you want to use the name attribute) is .getElementsByName() (not .getElementByName())

edited Apr 17, 2013 at 17:05

answered Apr 17, 2013 at 16:59

Jason Sperske

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3 Comments

user2291730 Over a year ago

Perfect! Thank you so much! But what was the bug?

user2291730 Over a year ago

Ok got it! Thank you for your help! haha such a simple mistake I over looked.

Jason Sperske Over a year ago

Your first draft just had the extra ), otherwise it was perfect (you should use Firefox+Firebug or Chrome to develop JavaScript it will tell you when there are syntax errors and exactly what they are)

MG_Bautista · Accepted Answer · 2013-04-17 16:49:59Z

0

Use

document.getElementByName('answer').value = ans;

answered Apr 17, 2013 at 16:49

MG_Bautista

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2 Comments

user2291730 Over a year ago

I tried this and the answer still does not show up in the BMI box

Jason Sperske Over a year ago

The function is called getElementsByName(), because it can return more than one: developer.mozilla.org/en-US/docs/DOM/document.getElementsByName

Pradeep Simha · Accepted Answer · 2013-04-17 16:50:07Z

0

You need to use document.getElementById() to get value of an HTML element, Change this:

document.bmi.answer.value = ans;

To:

document.getElementById('answer').value = ans;

This should work.

answered Apr 17, 2013 at 16:50

Pradeep Simha

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2 Comments

user2291730 Over a year ago

thanks for the quick response. I changed it but the answer still does not show up in the BMI input box.

Pradeep Simha Over a year ago

@user2291730, it's not getElementByName it should be getElementById() see my answer.. :) and you don't have id attribute for answer, add it.

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