Problem with Opera an IE

[Si]

Hi,

I'll start by saying I'm a complete newbie, this is the first time I
have used Javascript.

The code below I have written to calculate distance/bearings and times
from a grid reference.

It works absolutely fine in Opera 7.11, but in IE it throws up an
"object doesn't support this operation or method" error.

Any help/suggestions to where I have gone wrong and how I can get this
working in IE would be greatly appreciated.

Cheers Si,

############### CODE########### ########

function distance(form) {
var x1 = eval(form.x1.va lue);
var y1 = eval(form.y1.va lue);
var x2 = eval(form.x2.va lue);
var y2 = eval(form.y2.va lue);
var sd = eval(form.s.val ue);
var xdiff = x2 - x1;
var ydiff = y2 - y1;
var y = Math.pow((xdiff * xdiff + ydiff * ydiff), 0.5)/10;
if (Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) - 90 < 0) {
var b = Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) + 270;
}
else {
var b = Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) - 90;
}
var t = y / sd;
form.distance.v alue = Math.round(10*y )/10
form.time.value = (Math.round(10* t)/10)*60
form.bear.value = Math.round(b)
}
############### ############### #############

[Lasse Reichstein Nielsen]

Re: Problem with Opera an IE

s.e.r@cwcom.net (Si) writes:
[color=blue]
> The code below I have written to calculate distance/bearings and times
> from a grid reference.
>
> It works absolutely fine in Opera 7.11, but in IE it throws up an
> "object doesn't support this operation or method" error.[/color]

It would be very helpful to know which line the error comes from,
what the form contains and how the function is called.

[color=blue]
>
> function distance(form) {
> var x1 = eval(form.x1.va lue);[/color]

The "eval" function is a very slow way to turn a string into a number
(by a factor of 80 in some browsers). The fastest way us to use a
unary prefix plus. I.e.,

var x1 = +(form.x1.value );

You will probably never need to use "eval" for anything. There are
better and faster ways of solving most problems that a normal page
author runs into. Don't trust solutions that use "eval".
[color=blue]
> form.distance.v alue = Math.round(10*y )/10[/color]

You have an input element with the name "distance". IE makes a global
variable with that name that refers to the input element. However,
that overwrites your function called "distance". Change the name
of either the input element or the function.

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

[Si]

Re: Problem with Opera an IE

Lasse,

I Changed both things you suggested and it works great now.

Many Thanks.

Si,



Lasse Reichstein Nielsen <lrn@hotpop.com > wrote in message news:<r80t7xxp. fsf@hotpop.com> ...[color=blue]
> s.e.r@cwcom.net (Si) writes:
>[color=green]
> > The code below I have written to calculate distance/bearings and times
> > from a grid reference.
> >
> > It works absolutely fine in Opera 7.11, but in IE it throws up an
> > "object doesn't support this operation or method" error.[/color]
>
> It would be very helpful to know which line the error comes from,
> what the form contains and how the function is called.
>
>[color=green]
> >
> > function distance(form) {
> > var x1 = eval(form.x1.va lue);[/color]
>
> The "eval" function is a very slow way to turn a string into a number
> (by a factor of 80 in some browsers). The fastest way us to use a
> unary prefix plus. I.e.,
>
> var x1 = +(form.x1.value );
>
> You will probably never need to use "eval" for anything. There are
> better and faster ways of solving most problems that a normal page
> author runs into. Don't trust solutions that use "eval".
>[color=green]
> > form.distance.v alue = Math.round(10*y )/10[/color]
>
> You have an input element with the name "distance". IE makes a global
> variable with that name that refers to the input element. However,
> that overwrites your function called "distance". Change the name
> of either the input element or the function.
>
> /L[/color]

[Dr John Stockton]

Re: Problem with Opera an IE

JRS: In article <a7e8542a.03103 11546.241687ca@ posting.google. com>, seen
in news:comp.lang. javascript, Si <s.e.r@cwcom.ne t> posted at Fri, 31 Oct
2003 15:46:09 :-[color=blue]
>
>if (Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) - 90 < 0) {
>var b = Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) + 270;
>}
>else {
>var b = Math.atan2((y2 - y1),-(x2 - x1)) * (180 / Math.PI) - 90;
>}[/color]


If that's to convert (X, Y) to bearing from North, there must be an
easier way. Try exchanging X & Y, to get +-180 deg from North.

B = Math.atan2(X, Y)*180/Math.PI // -180<B<=+180
B = (360+Math.atan2 (X, Y)*180/Math.PI)%360 // 0<=B<360

Unless the span is certainly small, you should warn about approximations
die to the Non-Flat Earth.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> JS maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/JS/&c., FAQ topics, links.