eval

[Stuart]

why won't the following work

for(var i=0;i<pics;i++) {
eval('img'+i) = new Image(wth,hgt)
eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
}

basically I am trying to create a numer of placeholders with thier
associated imgages!

thanks in advance
stuart

[Douglas Crockford]

Re: eval

> why won't the following work[color=blue]
>
> for(var i=0;i<pics;i++) {
> eval('img'+i) = new Image(wth,hgt)
> eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> }[/color]

Where did you get this code?

[Stuart]

Re: eval


Douglas Crockford <nospam@laserli nk.net> wrote in message
news:55f44$3fa9 5a14$436563ac$1 5511@msgid.mega newsservers.com ...[color=blue][color=green]
> > why won't the following work
> >
> > for(var i=0;i<pics;i++) {
> > eval('img'+i) = new Image(wth,hgt)
> > eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> > }[/color]
>
> Where did you get this code?[/color]

It is part of a bigger script that I am writting, the problem that I am
facing is that I cannot asign the src value to a constucted variable

I need to create a variable amount of placeholders and cache images such as

img1 = new Image(100,200)
img1.src = 'someURL'
img2 = new Image(100,200)
img2.src = 'someURL'
img3 = new Image(100,200)
img3.src = 'someURL'

I am trying to construct the placeholder through a loop as folows

for(var i=1;i<pics;i++) {
( img + i ) = new Image(100,200)
(img + i).src = 'someURL'
}

what I don't know is how to join img and i

[Thomas 'PointedEars' Lahn]

Re: eval

Stuart wrote:
[color=blue]
> why won't the following work[/color]

Because it's evil[tm] eval(...). Besides, you are neither telling what you
are consider working nor what `pics' aso. are. Nevertheless, despite its
bad style, the below code does create Image objects and assigns a value to
their `src' property, so I consider it working.
[color=blue]
> for(var i=0;i<pics;i++) {
> eval('img'+i) = new Image(wth,hgt)
> eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> }
>
> basically I am trying to create a numer of placeholders with thier
> associated imgages![/color]

Provided that `pics' stores the number of Image objects to create, that
`wth' and `hgt' are values for the width and height of *each* object and
that the image resources to be accessed are available via the URLs
http://www.mypics/X1.gif, where X is a number from 0 to pics - 1, use

var myImages = new Object();
for (var i = 0; i < pics; i++)
{
myImages['img' + i] = new Image(wth, hgt);
myImages['img' + i].src = 'http://www.mypics/' + i + '1.gif';
}

instead.


PointedEars

[Douglas Crockford]

Re: eval

> > > why won't the following work[color=blue][color=green][color=darkred]
> > >
> > > for(var i=0;i<pics;i++) {
> > > eval('img'+i) = new Image(wth,hgt)
> > > eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> > > }[/color]
> >
> > Where did you get this code?[/color]
>
> It is part of a bigger script that I am writting, the problem that I am
> facing is that I cannot asign the src value to a constucted variable[/color]

Who told you to use eval()?

[Thomas 'PointedEars' Lahn]

Re: eval

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> Stuart wrote:[color=green]
>> why won't the following work[/color]
>
> Because it's evil[tm] eval(...). Besides, you are neither telling what you
> are consider working nor what `pics' aso. are. Nevertheless, despite its
> bad style, the below code does create Image objects and assigns a value to
> their `src' property, so I consider it working.
>[color=green]
>> for(var i=0;i<pics;i++) {
>> eval('img'+i) = new Image(wth,hgt)
>> eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
>> }[/color][/color]

Hm, having tested it in Mozilla 1.5b and IE 6.0 SP-1, I'm getting a script
error because eval(...) isn't allowed as left-hand side expression (IE says
explicitely: "Cannot assign to a result of a function" (or similar,
translated it from German). Maybe I'm mixing up something here, but I
remember ECMAScript implementations where it was possible to use it there.
However, it's still bad style.


PointedEars

[Stuart]

Re: eval


Douglas Crockford <nospam@laserli nk.net> wrote in message
news:8a03$3fa95 f61$436563ac$15 733@msgid.megan ewsservers.com. ..[color=blue][color=green][color=darkred]
> > > > why won't the following work
> > > >
> > > > for(var i=0;i<pics;i++) {
> > > > eval('img'+i) = new Image(wth,hgt)
> > > > eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> > > > }
> > >
> > > Where did you get this code?[/color]
> >
> > It is part of a bigger script that I am writting, the problem that I am
> > facing is that I cannot asign the src value to a constucted variable[/color]
>
> Who told you to use eval()?
>[/color]
I am trying anything....inc luding asking you!
Are you getting the jist of what I am trying to achieve?

[Stuart]

Re: eval


Thomas 'PointedEars' Lahn <PointedEars@we b.de> wrote in message
news:bobnnp$1cg hhm$1@ID-107532.news.uni-berlin.de...[color=blue]
> Thomas 'PointedEars' Lahn wrote:
>[color=green]
> > Stuart wrote:[color=darkred]
> >> why won't the following work[/color]
> >
> > Because it's evil[tm] eval(...). Besides, you are neither telling what[/color][/color]
you[color=blue][color=green]
> > are consider working nor what `pics' aso. are. Nevertheless, despite its
> > bad style, the below code does create Image objects and assigns a value[/color][/color]
to[color=blue][color=green]
> > their `src' property, so I consider it working.
> >[color=darkred]
> >> for(var i=0;i<pics;i++) {
> >> eval('img'+i) = new Image(wth,hgt)
> >> eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> >> }[/color][/color]
>
> Hm, having tested it in Mozilla 1.5b and IE 6.0 SP-1, I'm getting a script
> error because eval(...) isn't allowed as left-hand side expression (IE[/color]
says[color=blue]
> explicitely: "Cannot assign to a result of a function" (or similar,
> translated it from German). Maybe I'm mixing up something here, but I
> remember ECMAScript implementations where it was possible to use it there.
> However, it's still bad style.
>[/color]
Yes, I am getting these exact same errors,. However, I am pleased you
understood what I am trying to do, May be it is "bad style" but I am new to
javaScript, so may be you could point me in the way of "Good Style" and the
correct way of scripting.

[Lee]

Re: eval

Stuart said:[color=blue]
>
>
>Douglas Crockford <nospam@laserli nk.net> wrote in message
>news:55f44$3fa 95a14$436563ac$ 15511@msgid.meg anewsservers.co m...[color=green][color=darkred]
>> > why won't the following work
>> >
>> > for(var i=0;i<pics;i++) {
>> > eval('img'+i) = new Image(wth,hgt)
>> > eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
>> > }[/color]
>>
>> Where did you get this code?[/color]
>
>It is part of a bigger script that I am writting, the problem that I am
>facing is that I cannot asign the src value to a constucted variable
>
>I need to create a variable amount of placeholders and cache images such as
>
>img1 = new Image(100,200)
>img1.src = 'someURL'
>img2 = new Image(100,200)
>img2.src = 'someURL'
>img3 = new Image(100,200)
>img3.src = 'someURL'
>
>I am trying to construct the placeholder through a loop as folows
>
>for(var i=1;i<pics;i++) {
> ( img + i ) = new Image(100,200)
> (img + i).src = 'someURL'
>}
>
>what I don't know is how to join img and i[/color]

Whenever you find yourself using eval(), you've probably
overlooked a simpler way to do something.

var img=new Array();
for(var i=0;i<pics;i++) {
img[i] = new Image(100,200);
img[i].src = 'someURL';
}

[Douglas Crockford]

Re: eval

> > Who told you to use eval()?[color=blue][color=green]
> >[/color]
> I am trying anything....inc luding asking you!
> Are you getting the jist of what I am trying to achieve?[/color]

It is almost always extremely wrong to use eval(). Who is teaching you to
program so badly?

[Janwillem Borleffs]

Re: eval


"Stuart" <kffgtr@yytd.gf t> schreef in bericht
news:bobmgv$95i $1@newsg4.svr.p ol.co.uk...[color=blue]
>
> I am trying to construct the placeholder through a loop as folows
>
> for(var i=1;i<pics;i++) {
> ( img + i ) = new Image(100,200)
> (img + i).src = 'someURL'
> }
>
> what I don't know is how to join img and i
>[/color]

Try it as follows:

for(var i=1;i<pics;i++) {
window['img' + i] = new Image(100,200)
window['img' + i].src = 'someURL'
}


JW

[Thomas 'PointedEars' Lahn]

Re: eval

Stuart wrote:

[Repaired quoting, please read

http://home.in.tum.de/~jain/software/oe-quotefix/]

[color=blue]
> Thomas 'PointedEars' Lahn <PointedEars@we b.de> wrote [...][color=green]
>> Thomas 'PointedEars' Lahn wrote:
>> [...] May be it is "bad style" but I am new to
>> javaScript, so may be you could point me in the way of "Good Style" and the
>> correct way of scripting.[/color][/color]

I already did, what part of it did you not understand?

Maybe if you would shorten the quotes to what is required for following the
discussion, which saves disk space and bandwidth, and eases reading, you
were forced to read postings more thoroughly:

http://www.albion.com/netiquette/corerules.html

PointedEars

[Thomas 'PointedEars' Lahn]

Re: eval

Stuart wrote:
[color=blue]
> Thomas 'PointedEars' Lahn <PointedEars@we b.de> wrote [...][color=green]
> > However, [eval(...) is] still bad style.[/color]
>
> [...] May be it is "bad style" but I am new to javaScript, so may be you
> could point me in the way of "Good Style" and the correct way of
> scripting.[/color]

I already did, what part of it did you not understand?

Maybe if you would shorten the quotes to what is required for following the
discussion, which saves disk space and bandwidth, and eases reading, you
were forced to read postings more thoroughly:

http://www.albion.com/netiquette/corerules.html

HTH

PointedEars

[Stuart]

Re: eval

Many thanks Lee.....works perfectly

thanks again
Stuart


Lee <REM0VElbspamtr ap@cox.net> wrote in message
news:bobnfk0jkg @drn.newsguy.co m...[color=blue]
> Stuart said:[color=green]
> >
> >
> >Douglas Crockford <nospam@laserli nk.net> wrote in message
> >news:55f44$3fa 95a14$436563ac$ 15511@msgid.meg anewsservers.co m...[color=darkred]
> >> > why won't the following work
> >> >
> >> > for(var i=0;i<pics;i++) {
> >> > eval('img'+i) = new Image(wth,hgt)
> >> > eval('img'+i+'. src') = 'http://www.mypics/'+i+'1.gif'
> >> > }
> >>
> >> Where did you get this code?[/color]
> >
> >It is part of a bigger script that I am writting, the problem that I am
> >facing is that I cannot asign the src value to a constucted variable
> >
> >I need to create a variable amount of placeholders and cache images such[/color][/color]
as[color=blue][color=green]
> >
> >img1 = new Image(100,200)
> >img1.src = 'someURL'
> >img2 = new Image(100,200)
> >img2.src = 'someURL'
> >img3 = new Image(100,200)
> >img3.src = 'someURL'
> >
> >I am trying to construct the placeholder through a loop as folows
> >
> >for(var i=1;i<pics;i++) {
> > ( img + i ) = new Image(100,200)
> > (img + i).src = 'someURL'
> >}
> >
> >what I don't know is how to join img and i[/color]
>
> Whenever you find yourself using eval(), you've probably
> overlooked a simpler way to do something.
>
> var img=new Array();
> for(var i=0;i<pics;i++) {
> img[i] = new Image(100,200);
> img[i].src = 'someURL';
> }
>[/color]

[Stuart]

Re: eval


Douglas Crockford <nospam@laserli nk.net> wrote in message
news:2a40e$3fa9 6685$436563ac$1 6169@msgid.mega newsservers.com ...[color=blue][color=green][color=darkred]
> > > Who told you to use eval()?
> > >[/color]
> > I am trying anything....inc luding asking you!
> > Are you getting the jist of what I am trying to achieve?[/color]
>
> It is almost always extremely wrong to use eval(). Who is teaching you to
> program so badly?
>[/color]

And your input has been ?????