# Simple JavaScript **URL:** \ **Category:** web dev\ **Created:** [April 12, 2006, 4:55pm UTC](https://forum.kirupa.com/t/simple-javascript/185343 "2006-04-12T16:55:32Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![camargo](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/camargo/32/1363_2.png) [@camargo](https://forum.kirupa.com/u/camargo)\ **Post date:** [April 12, 2006, 4:55pm UTC](https://forum.kirupa.com/t/simple-javascript/185343/1 "2006-04-12T16:55:32Z")
Hey Kirupans! I have a question about some JavaScript. I’m trying to make a very very simple calculator. The user enters a number, it processes an equation, then BOOM! They get an answer. It all takes place in one form. Here’s a link to the simple page: [http://www.wirelessinteractive.com/calculator.html](http://www.wirelessinteractive.com/calculator.html) Now the JavaScript looks like this: ```auto function lmr100(calc){ var FMHz = calc.FMHz.value; var sFMHz = Math.sqrt(FMHz); var atten = (0.70914) * (sFMHz) + (0.00174) * (FMHz); calc.atten.value = atten; return false; } ``` And my form looks like this: ```auto
FMHz:
Attenuation:
``` Again, all very simple. Yet for some reason, when click on that button, I get an error that says “form” is undefined. Am I missing something? ---
**Author:** ![camargo](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/camargo/32/1363_2.png) [@camargo](https://forum.kirupa.com/u/camargo)\ **Post date:** [April 12, 2006, 5:00pm UTC](https://forum.kirupa.com/t/simple-javascript/185343/2 "2006-04-12T17:00:29Z")
Hmm… Ok, I feel like a bonehead… I needed to change: ```auto onClick="lmr100()" ``` to this: ```auto onClick="lmr100(calc)" ``` ---
**Author:** ![camargo](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/camargo/32/1363_2.png) [@camargo](https://forum.kirupa.com/u/camargo)\ **Post date:** [April 12, 2006, 7:07pm UTC](https://forum.kirupa.com/t/simple-javascript/185343/3 "2006-04-12T19:07:11Z")
Ok, so here’s a new question. I’ve got a drop down menu on the form. I’d like to run a different function depending on the value of the drop down menu. Is that possible? Here’s the link again: [http://www.wirelessinteractive.com/calculator.html](http://www.wirelessinteractive.com/calculator.html) ---
**Author:** ![Ankou](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/ankou/32/1351_2.png) [@Ankou](https://forum.kirupa.com/u/Ankou)\ **Post date:** [April 12, 2006, 8:00pm UTC](https://forum.kirupa.com/t/simple-javascript/185343/4 "2006-04-12T20:00:17Z")
Sure it’s possible. Just taking a brief look at your page you could do something like… When the button is clicked for calculate you call the function lmr100(calc). In that function check the value of the drop down menu. Depending on that value, select the function that you want to use for the calculation… Here’s just a simple example: ```auto
Number 1:

Number 2:
Answer:
``` There aren’t any checks in there to make sure the values being input are numerical, but that should be done to prevent errors. A simple regular expression test could look for number characters and the . and - (for decimal values and negative values).