Switch() Statement Not Working

rdavis7408

Hello, I have four textboxes that the user enters the price per gallon
paid at the pump, the mileage per gallon and I would like to then
calculate the cost per gallon and use a switch statement to pull a
value based on the price per gallon.

For example if the price of fuel is 2.44 per gallon and the enter that
they get 5.9 miles per gallon the cost of that mile is $.41. Then based
on the cost per gallon of 2.44 we might pay them another $.20 per
gallon based off of the numbers in the switch statement.

The calculation worked until I added the switch statement. Why is that?
Can anyone help?

Thanks ahead of time. Below is the script:

<html>
<head>
<title>Untitl ed Document</title>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<link href="fsc.css" rel="stylesheet " type="text/css">
</head>

<body>

<script language="JavaS cript">
function FuelCalculator( f)
{
var A;
A= Math.round((f.p pg.value/f.mpg.value)*10 0);
f.cpg.value = "$"+(A/100);
}

var b;
b=this.form.ppg .value
switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;
Case >=1.31 && <=1.369:
this.form.dlnt. value=.02;
Case >=1.37 && <=1.429:
this.form.dlnt. value=.03;
default:
this.form.dlnt. value=.99

}

</script>

<form action="">

<table width="351">
<tr>
<td width="213"> Cents per gallon:</td>
<td width="60" > <input name="ppg" type="text"
style="text-align:center" value="0" size="10">
</td>
</tr>
<tr>
<td>Miles per gallon:</td>
<td> <input name="mpg" type="text" value="0" size="10"
style="text-align:center">
</td>
</tr>
<tr>
<td>Fuel Cost Per Mile: </td>
<td > <input name="cpg" type= "text" disabled="true" value="0"
size="10" style="text-align:center">
</td>
<tr>
<td>Dillon Fuel Surcharge Payment: </td>
<td> <input name="dlnt" type="text" disabled="true" value="0"
size="10" style="text-align:center">
</td>
<tr>
<td colspan="2" ><input name="button" type="button"
onClick="FuelCa lculator(this.f orm);" value="Calclula te"> </td>
</tr>
<td><input name="FSC" type="button" onClick="switch (b)"
value="FSC"></td>

</table>

</form>
</body>
</html>

Jan 31 '06 #1

Subscribe Reply

3803

Evertjan.

wrote on 31 jan 2006 in comp.lang.javas cript:

switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;

It is all in the name:

case is lowercase!

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

Jan 31 '06 #2

Evertjan.

Evertjan. wrote on 31 jan 2006 in comp.lang.javas cript:

wrote on 31 jan 2006 in comp.lang.javas cript:
switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;

It is all in the name:

case is lowercase!

and give me a break:

you will have to use break;

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

Jan 31 '06 #3

web.dev

rd********@gmai l.com wrote:

<script language="JavaS cript">
The language attribute is deprecated, use the type attribute instead:

<script type = "text/javascript">
b=this.form.ppg .value
This statement is error-prone. Instead give your form a name and
access its elements in the following fashion:

var b = document.forms["formName"].elements["ppg"].value;
switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;
Case >=1.31 && <=1.369:
this.form.dlnt. value=.02;
Case >=1.37 && <=1.429:
this.form.dlnt. value=.03;
default:
this.form.dlnt. value=.99

}

1. It is not 'Case', but should be 'case' with a lowercase C.
2. You should have a 'break' after one or more cases. And a 'break'
after the default case.
3. The switch construct does not deal with a range of values. You
should instead use if...else statements instead.

var dintVal = .99;

if(b >= 1.25 && b <= 1.3)
{
dintVal = .01
}
else if(b >= 1.31 && b <= 1.369)
{
dintVal = .02
}
else if(b >= 1.37 && b <= 1.429)
{
dintVal = .03;
}

document.forms["formName"].elements["dInt"].value = dintVal;

Jan 31 '06 #4

Lasse Reichstein Nielsen

rd********@gmai l.com writes:

The calculation worked until I added the switch statement. Why is that? switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;
Case >=1.31 && <=1.369:
this.form.dlnt. value=.02;
Case >=1.37 && <=1.429:
this.form.dlnt. value=.03;
default:
this.form.dlnt. value=.99

}

You are guessing blindly. That rarely works in programming, since
computers are notoriously bad at guessing what you really meant.

The syntax of a case statement is:
case <expression>: <statement>

Example:

switch(num){
case 1: // something for 1
break;
case 2: case 3: // something for 2 or 3
break;
default: // ...
}

In your case, you want to match intervals, not values, so
a switch statement isn't the immediate choice. Instead
use a sequence of if-statements:

if (b >= 1.25 && b <= 1.30) {
this.form.dlnt. value=.01;
} else if (b > 1.30 && b < 1.37) {
...
} else if (b >= 1.37 && b < 1.43) {
...
} else {
...
}
You can get the same effect with a switch, but it's not really
smarter, and it's much less readable.

switch(true) {
case (b >= 1.25 && b <= 1.30) :
this.form.dlnt. value=.01;
break;
case (b > 1.30 && b < 1.37) :
...
break;
...
}

/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

Feb 1 '06 #5

Hal Rosser

<rd********@gma il.com> wrote in message
news:11******** **************@ g49g2000cwa.goo glegroups.com.. .

Hello, I have four textboxes that the user enters the price per gallon
paid at the pump, the mileage per gallon and I would like to then
calculate the cost per gallon and use a switch statement to pull a
value based on the price per gallon.

For example if the price of fuel is 2.44 per gallon and the enter that
they get 5.9 miles per gallon the cost of that mile is $.41. Then based
on the cost per gallon of 2.44 we might pay them another $.20 per
gallon based off of the numbers in the switch statement.

The calculation worked until I added the switch statement. Why is that?
Can anyone help?

Thanks ahead of time. Below is the script:

<html>
<head>
<title>Untitl ed Document</title>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<link href="fsc.css" rel="stylesheet " type="text/css">
</head>

<body>

<script language="JavaS cript">
function FuelCalculator( f)
{
var A;
A= Math.round((f.p pg.value/f.mpg.value)*10 0);
f.cpg.value = "$"+(A/100);
}

var b;
b=this.form.ppg .value
switch(b)
{
Case >=1.25 && <=1.30:
this.form.dlnt. value=.01;
Case >=1.31 && <=1.369:
this.form.dlnt. value=.02;
Case >=1.37 && <=1.429:
this.form.dlnt. value=.03;
default:
this.form.dlnt. value=.99

}

</script>

<form action="">

<table width="351">
<tr>
<td width="213"> Cents per gallon:</td>
<td width="60" > <input name="ppg" type="text"
style="text-align:center" value="0" size="10">
</td>
</tr>
<tr>
<td>Miles per gallon:</td>
<td> <input name="mpg" type="text" value="0" size="10"
style="text-align:center">
</td>
</tr>
<tr>
<td>Fuel Cost Per Mile: </td>
<td > <input name="cpg" type= "text" disabled="true" value="0"
size="10" style="text-align:center">
</td>
<tr>
<td>Dillon Fuel Surcharge Payment: </td>
<td> <input name="dlnt" type="text" disabled="true" value="0"
size="10" style="text-align:center">
</td>
<tr>
<td colspan="2" ><input name="button" type="button"
onClick="FuelCa lculator(this.f orm);" value="Calclula te"> </td>
</tr>
<td><input name="FSC" type="button" onClick="switch (b)"
value="FSC"></td>

</table>

</form>
</body>
</html>

It appears you are mixing VB's "Select case" syntax with Javascript's
"switch" syntax, and the result is you missed'em both. Easy mistake - take
a look at
http://devguru.com for a reference on both VB and Javascript.

Feb 1 '06 #6

Thomas 'PointedEars' Lahn

Hal Rosser wrote:

[Full quote]
<http://jibbering.com/faq/faq_notes/pots1.html#ps1P ost>
It appears you are mixing VB's "Select case" syntax with Javascript's
"switch" syntax, and the result is you missed'em both. Easy mistake -
take a look at
http://devguru.com for a reference on both VB and Javascript.

devguru.com contains a lot of factually incorrect and obsolete
information about JS/ECMAScript and is therefore not recommended.
PointedEars

Feb 1 '06 #7

Thomas 'PointedEars' Lahn

web.dev wrote:

rd********@gmai l.com wrote:
b=this.form.ppg .value
This statement is error-prone.

Nonsense.
Instead give your form a name and access its elements in the following
fashion:

var b = document.forms["formName"].elements["ppg"].value;

No, the approach using the `form' property was the better one, however it
only works if used in the right place.

<meta http-equiv="Content-Script-Type" content="text/javascript">
...
<script type="text/javascript">
function fuelCalculator( o)
{
var es;
if (o && o.form && (es = o.form.elements ))
{
var b = +es['ppg'].value;
var A = Math.round((b / es['mpg'].value) * 100);
es['cpg'].value = "$" + (A / 100);

var t = es['dlnt'];

// To use switch..case..d efault instead, one could use the
// Interval prototype from my JSX:math.js instead; it provides
// a getIntervalInde x() method which returns the numeric array
// index of the interval that contains a value.

if (b >= 1.25 && b <= 1.30)
{
t.value = 0.01;
}
else if (b >= 1.31 && b <= 1.369)
{
t.value = 0.02;
}
else if (b >= 1.37 && b <= 1.429)
{
t.value= 0.03;
}
else
{
t.value= 0.99;
}
}
}

document.write( '<input type="button" name="btn1"'
+ ' onclick="fuelCa lculator(this); ">');
</script>
PointedEars

Feb 1 '06 #8

web.dev

Thomas 'PointedEars' Lahn wrote:

web.dev wrote:
rd********@gmai l.com wrote:
b=this.form.ppg .value

This statement is error-prone.

Nonsense.
Instead give your form a name and access its elements in the following
fashion:

var b = document.forms["formName"].elements["ppg"].value;

No, the approach using the `form' property was the better one, however it
only works if used in the right place.

In his script, doesn't "this" reference the global window object?
Isn't that why it's error-prone? Otherwise, I do agree that
"this.form" would've been better if used in the right place.

Feb 1 '06 #9

Thomas 'PointedEars' Lahn

web.dev wrote:

Thomas 'PointedEars' Lahn wrote:
web.dev wrote:
> rd********@gmai l.com wrote:
>> b=this.form.ppg .value
>
> This statement is error-prone.
Nonsense.
> Instead give your form a name and access its elements in the following
> fashion:
>
> var b = document.forms["formName"].elements["ppg"].value;

No, the approach using the `form' property was the better one, however it
only works if used in the right place.

In his script, doesn't "this" reference the global window object?

It probably refers to the Global Object there. That is not necessarily a
Window object or the same object the global `window' property refers to.
Isn't that why it's error-prone?
AFAIK, it is an error in the context used by the OP, not only error-prone.
Or can you name any UA where it would work with the OP's HTML code?
Otherwise, I do agree that "this.form" would've been better if used in the
right place.

ACK
PointedEars

Feb 1 '06 #10

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