Validation?

**Hit** · May 26, 2002, 16:23

Hi, I've had to make a simple script to do simple calculations:

Code:

<script language=JavaScript>
function calculate()
{
document.calculator.answer.value=
eval(document.calculator.expression.value)
}
</script>

<form name="calculator">
<input type="text" size="20" name="expression">
<input type="button" value="Calculate" onclick="calculate()">
<input type="reset" value="Reset">
Answer:<input type="text" size="20" name="answer">
</form>

But, what I now want to do is validate it, so that if any letters of the alphabet are entered > then an alert comes up. So basically, all I want allowed is: numbers + - * / . ( )

I've tried to figure this out and searched everywhere on the net, but haven't found much! So is there a simple solution to this?

Thanks.

**MarcusJT** · May 26, 2002, 18:20

This is best approached using regular expressions. See these to get started (plenty more where that came from here):
http://www.oreillynet.com/pub/a/java...id.html?page=1
and
http://www.siteexperts.com/tips/func...ts23/page1.asp

M@rco

**Hit** · May 26, 2002, 18:50

Thanks M@rco, I've had a quick look at the links, but I'll try & work it out tomorrow now. I've had enough of staring at the computer screen for today!

**Hit** · May 27, 2002, 15:38

I've finally come up with the following, it seems ok:

Code:

<html>
<head>
<title>Using The Eval() Function</title>
<script>
<!--

function calculate() {
document.calculator.answer.value = eval(document.calculator.expression.value)
}


function checkInput(strng) {
var illegalChars= /[\a-z\A-Z\!\"\£\$\%\^\&\=\{\}\[\]\;\:\'\@\#\~\,\<\>\\\?\|\`]/;
 if (strng.match(illegalChars)) 
  {
   alert("Invalid Expression Entered!");
   document.calculator.expression.focus();
   document.calculator.expression.select();
   return false
  }
    return true
}


function focus() {
document.calculator.expression.focus();
}

// -->
</script>
</head>
<body onload=focus()>
<basefont=3>
<font face=verdana size=-1> <center> <b>Using The Eval() Function</b> </center> </font> <p>
<font face=verdana size=-2>

<form name="calculator">
Please enter a valid mathematical expression: <input type="text" size="15" name="expression">
<input type="button" value="Calculate" onClick="if (checkInput(document.calculator.expression.value)) { calculate(this.form) }">
<input type="reset" value="Reset"> 
Answer = <input type="text" size="15" name="answer">
</form>

</font>
</body>
</html>

Thanks again for the help M@rco.

**MarcusJT** · May 27, 2002, 17:58

You're welcome! Handy, aren't they? (RegExs)

M@rco

**Hit** · May 27, 2002, 18:14

Yeah they are, I've come across them before, but didn't know what they were called & didn't really know how to use them...

So, I guess everything seems allright in my scripts above?

**MarcusJT** · May 28, 2002, 04:25

It seems fine (only had a quick play because I'm in the middle of my Uni finals)!

M@rco

**Hit** · May 28, 2002, 14:08

Cool. Good Luck with your exams (I HATE exams).

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