Array in javascript

L

Leszek

Hi.

Is it possible in javascript to operate on an array without knowing how mamy
elements it has?
What i want to do is sending an array to a script, and this script should
add all values from that array

Could you show me a little example how to do this?

Thanks.
Leszek
 
T

Thomas 'PointedEars' Lahn

Leszek said:
Is it possible in javascript to operate on an array without knowing how
mamy elements it has?
Click to expand...

Of course. This is what the e.g. `length' property of Array objects is for.
What i want to do is sending an array to a script, and this
script should add all values from that array

Could you show me a little example how to do this?
Click to expand...

Depends on what you mean by "sending an array to a script" (which array,
which script, client-side or server-side, send from where to where?) and by
"script should add all values from that array" (add from where exactly to
which?)


PointedEars
 
V

VK

Leszek said:
Hi.

Is it possible in javascript to operate on an array without knowing how mamy
elements it has?
Click to expand...

JavaScript array is Dynamic Sparse Jagged Array. That can be too much
of adjectives for one time :) but the first one means that can add new
elements to array without ReDim / resize() it.

var myArray = new Array(); // 0 elements
myArray[0] = 0;
....
....
myArray[1000] = 1000;

About other adjectives (and about JavaScript arrays at whole) you can
read at:
What i want to do is sending an array to a script, and this script should
add all values from that array
Could you show me a little example how to do this?
Click to expand...

As it was pointed out it depends on how and in what form are you
getting the original data for your array.
 
G

Guillaume

Leszek
Is it possible in javascript to operate on an array without knowing how mamy
elements it has?
Click to expand...

I don't think, there is no function like 'map' or 'apply'. However, they
are not difficult to implement because you always know the size of an
array: array.length;
 
T

Thomas 'PointedEars' Lahn

VK said:
JavaScript array is Dynamic Sparse Jagged Array. That can be too much
of adjectives for one time :)
Click to expand...

But I am sure you can invent more just to cover your lack of knowledge and
understanding of the basics.
but the first one means that can add new
elements to array without ReDim / resize() it.

var myArray = new Array(); // 0 elements
myArray[0] = 0;
...
...
myArray[1000] = 1000;
Click to expand...

You did not answer the question of the OP _at all_. Figures.
About other adjectives (and about JavaScript arrays at whole) you can
read at:
<http://www.geocities.com/schools_ring/ArrayAndHash.html>
Click to expand...

This text contains a lot of, if not consists mainly of, factually incorrect
information, presented as being the truth despite of that. Readers are
strongly recommended to ignore it, to handle all statements of its author
regarding (proper) software development with extreme care, and to read
previous discussions on the subject instead.

<URL:http://groups.google.com/groups?as_q=Array&as_ugroup=comp.lang.javascript&scoring=d&filter=0>
<URL:http://groups.google.com/groups?as_uauthors=VK&as_ugroup=comp.lang.javascript&scoring=d&filter=0>


PointedEars
 
J

Jambalaya

Leszek said:
Hi.

Is it possible in javascript to operate on an array without knowing how mamy
elements it has?
Yes.

What i want to do is sending an array to a script, and this script should
add all values from that array

Could you show me a little example how to do this?
Click to expand...

This is the smallest example I could write:

<html><head><title>Little Sum Function</title></head>
<body><script type="text/javascript">
function s(a){return Function('return '+a.join('+'))()}
document.write(s([1,654,2,5,489,51,3851,681,32,5,0]))
</script></body></html>
 
V

VK

Thomas said:
But I am sure you can invent more just to cover your lack of knowledge and
understanding of the basics.
Click to expand...

JavaScript array is Dinamic, is Sparse and is Jagged. These three core
features are important to know to operate properly with arrays and get
expected results.

<http://www.geocities.com/schools_ring/ArrayAndHash.html> is the only
one known (to me at least) resource there all three features along with
other information would be named and illustrated properly: all within
the same page. Unfortunately (after careful reading and searching) this
is still the only resource I can endorse for JavaScript array
information.

It should be updated though by removing some no so relevant part at the
bottom and by adding new array methods from JavaScript 1.6 (Firefox 1.5)
 
T

Thomas 'PointedEars' Lahn

Jambalaya said:
Leszek said:
What i want to do is sending an array to a script, and
this script should add all values from that array

Could you show me a little example how to do this?
Click to expand...

This is the smallest example I could write:

<html>
<head><title>Little Sum Function</title></head>
<body><script type="text/javascript">
function s(a){return Function('return '+a.join('+'))()}
document.write(s([1,654,2,5,489,51,3851,681,32,5,0]))
</script></body></html>
Click to expand...

Nice[1] :)

Not shorter, but Valid:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd"><head><meta
http-equiv="Content-Type" content="text/html;charset=ISO-8859-1">
<title>Little Adder</title></head><script
type="text/javascript">document.write(Function("return "
+[1,654,2,5,489,51,3851,681,32,5,0].join("+"))());</script>


Regards,
PointedEars
___________
[1] especially because there is no evil[tm] eval()
 
E

Evertjan.

Jambalaya wrote on 02 feb 2006 in comp.lang.javascript:
This is the smallest example I could write:

<html><head><title>Little Sum Function</title></head>
<body><script type="text/javascript">
function s(a){return Function('return '+a.join('+'))()}
document.write(s([1,654,2,5,489,51,3851,681,32,5,0]))
</script></body></html>
Click to expand...

<script type="text/javascript">
alert(eval([1,654,2,5,489,51,3851,681,32,5,0].join('+')));
</script>

or for the (eval==evil)-ers:

<script type="text/javascript">
var b=0,a=[1,654,2,5,489,51,3851,681,32,5,0],z=a.length;
while(z)b+=a[--z];alert(b)
</script>
 
R

RobG

Leszek wrote:
[...]
What i want to do is sending an array to a script, and this script should
add all values from that array

Could you show me a little example how to do this?
Click to expand...

// An array of numbers, some as strings
var A = [2,'5',8,'2',4];

// A function that adds all the elements of an array
function addEm(X)
{
var i = X.length;
var sum = 0;
while(i--) sum += +X;
return sum;
}

// Show it in action
alert( addEm(A) );


If there is any chance that some of the elements might not be numbers,
then that should be checked before attempting addition:

var A = [2,'blah','5',8,2,4];

function addEm(X)
{
var x, i = X.length;
var sum = 0;
while(i--) {
x = +X;
if ( !isNaN(x) ) sum += x;
}
return sum;
}
 
V

VK

Ian said:
I think the previous responses over looked the use of
for( var n in array ) {} as a method for iterating over an array.


function test( names )
{
for( var name in names )
{
// do something.
}
}
Click to expand...

for-in loop has nothing to do with *array*, it's an iterator over
enumerable properties of object.

Try this to understand the difference:

var arr = [1,2,3];
arr.foo = 'bar';

for (var i=0; i<arr.length; i++) {
alert(arr);
}

for (var p in arr) {
alert(p);
}
 
R

Richard Cornford

VK said:
JavaScript array is Dinamic, is Sparse and is Jagged.
Click to expand...

Can you justify applying the term "jagged" to a javascript array when
they can only have a single dimension?

<http://www.geocities.com/schools_ring/Array ...
Click to expand...
... . Unfortunately (after careful reading and searching)
this is still the only resource I can endorse for JavaScript
array information.
Click to expand...
<snip>

Your willingness to endorse your own page is not significant (beyond the
observation that your tendency to always choose the worst option
available means that your endorsement may be taken as a condemnation by
reasoning observers). The important consideration is whether it could be
endorsed by anyone who actually understands javascript. You have tried
to get such an endorsement from contributors to this group and the
reactions you got were anything but an endorsement.

Richard.
 
V

VK

Richard said:
Can you justify applying the term "jagged" to a javascript array when
they can only have a single dimension?
Click to expand...

This is exactly the case with JavaScript array wich is a single
dimension array when looking at it "from the top". But it can have
other arrays as its elements. Array of arrays is called in the
programming "jagged array".
We may of course continue to stay on the position that nothing of
regular programming is applicable to JavaScript - neither in terms nor
in technology :)
In such case array of arrays is called "jagged" everywhere but in
JavaScript it's just "array of arrays" :)

Jagged nature of JavaScript array is really important to know and
understand for say array sorting.
Your willingness to endorse your own page is not significant (beyond the
observation that your tendency to always choose the worst option
available means that your endorsement may be taken as a condemnation by
reasoning observers). The important consideration is whether it could be
endorsed by anyone who actually understands javascript. You have tried
to get such an endorsement from contributors to this group and the
reactions you got were anything but an endorsement.
Click to expand...

This article is not perfect and I willing to update it and make it even
more transparent. I would like to link some reputable public source
instead from say Mozilla.org or MSDN or IBM.com etc. Unfortunately
anything of this kind is either incomplete, or confusing or (more
often) factually wrong.
 
R

Richard Cornford

VK said:
This is exactly the case with JavaScript array wich is a single
dimension array when looking at it "from the top".
Click to expand...

Javascript has single dimension arrays however you look at them.
But it can have other arrays as its elements. Array of arrays
is called in the programming "jagged array".
Click to expand...

No, the concept of a jagged array can only be implemented in javascript
with an array of arrays, but that does not make the javascript array
jagged. Indeed, the very fact that you must have more than one Array in
order to implement the concept of 'jagged' means that the term _cannot_
apply to a javascript Array (singular).

And "in the programming" a 'jagged array' is not an array of arrays, as
is easily demonstrated by the Java array, which is a single array that
is multidimensional and jagged.
We may of course continue to stay on the position that nothing
of regular programming is applicable to JavaScript - neither
in terms nor in technology :)
Click to expand...

We? You are exclusively and personally responsible for your own
incoherent ramblings.
In such case array of arrays is called "jagged" everywhere
but in JavaScript it's just "array of arrays" :)
Click to expand...

Everywhere? I think you will find that the term 'jagged' will normally
be applied with discrimination beyond your comprehension.
Jagged nature of JavaScript array is really important to know
and understand for say array sorting.
Click to expand...

So it is important to understand that the javascript array is a single
dimension array and so cannot be 'jagged'.
This article is not perfect and I willing to update it and make
it even more transparent.
Click to expand...

BODY {
display:none;
}
I would like to link some reputable public source instead
from say Mozilla.org or MSDN or IBM.com etc.
Click to expand...

Bad sources of information often try to gain credibility by linking to
'reputable public sources'. What is up, you cannot find anything on
these sites that doesn't directly contradict your page?
Unfortunately anything of this kind is either incomplete, or
confusing or (more often) factually wrong.
Click to expand...

LOL. You own page is incomplete, confusing and factually wrong. That is
precisely what was said of it when you attempted to get this group to
endorse it.

On the other hand, one of the advantages of your page is that some of
the 'factually wrong' is so obvious that only the complete novice is
likely to give any credence to the rest of its text.

Richard.
 
V

VK

Richard said:
same old story
Click to expand...

All arguments has been spelled many times over the last year.
You are welcome to give array-related advises from your point of view:
and I reserve the same for mine.

Eventually only the practice (who's picture allow to create effective
predictable code) is the way to check a theory. A theory in
contradiction with the practical experience is worthless IMHO.
 
V

VK

Richard said:
No, the concept of a jagged array can only be implemented in javascript
with an array of arrays, but that does not make the javascript array
jagged. Indeed, the very fact that you must have more than one Array in
order to implement the concept of 'jagged' means that the term _cannot_
apply to a javascript Array (singular).
Click to expand...

Sorry for making addons to my post, but there is a logical (not
pragrammatical) error in the above reasonning:

Neither C++ or Java array are *obligated* to be multi-dimensional. In
any language I can perfectly create a simple single-dimention array.
Applying your own thesis: "The very fact that you must have more than
one dimension in order to implement the concept of `multi-dimensional'
means that the term _cannot_ apply to a C++ array (singular)."

This logical casus can be solved is we realize that "milti-dimensional"
vs. "jagged" are applied to the *model potention* and not to a
particular given array X, Y or Z.
 
R

Richard Cornford

VK said:
Sorry for making addons to my post, but there is a logical
(not pragrammatical) error in the above reasonning:
Click to expand...

It is partly the fact that you cannot recognise logical errors that
leads me to question your rationality.
Neither C++ or Java array are *obligated* to be multi-dimensional.
Click to expand...

While javascript Arrays cannot be multi-dimensional.
In any language I can perfectly create a simple
single-dimention array. Applying your own thesis:
"The very fact that you must have more than
one dimension in order to implement the concept of
`multi-dimensional' means that the term _cannot_ apply
to a C++ array (singular)."
Click to expand...

In that case the parallel statement is that because you have to have
more than one dimension before something is multi-dimensional then a
_dimension_ (singular) cannot be multi-dimensional. That is, the term
'multi-dimensiton' cannot be applied to a dimension.

The term is applicable to arrays in certain languages because they have
the potential to have multiple dimensions, whether the actually do or
not (and the Java array has the potential to be jagged as well).

It is like stating that the javascript Array is a sparse array. Actual
array instances do not need to be sparse (in the sense of having fewer
than - array.length - 'array index' properties), but the configuration
of an instance does not alter the nature of the javascript Array.
This logical casus can be solved is we realize that
"milti-dimensional" vs. "jagged" are applied to the
*model potention* and not to a particular given array
X, Y or Z.
Click to expand...

The javascript array has no potential to have multiple dimensions and so
no potential to be 'jagged'. Both concepts can be successfully
implemented/emulated with javascript but that can not be done with a
single javascript Array, and so the terms 'multi-dimensional' and
'jagged' are not applicable as characteristics of a javascript Array.

Richard.
 
R

Richard Cornford

VK said:
All arguments has been spelled many times over the
last year.
Click to expand...

Yes they have, and you have presented no reasoned counter argument, only
the stubborn refusal to pay any attention.
You are welcome to give array-related advises from
your point of view: and I reserve the same for mine.
Click to expand...

Your ability (and right) to post any nonsense you choose cannot be
denied. But your should have no expectation of being allowed to do so
without being criticised for doing so.

And I am subject to the same consideration. If I posted nonsense,
falsehoods and bad advice I expect (and even want) to be corrected and
criticised for doing so. But that doesn't seem to happen often; not
because I am intrinsically or inherently correct but because in the past
I have paid attention to such comments and learnt form them.

Initial ignorance of any subject is inevitable and as people learn they
make mistakes, but most learn form, instead of repeating, their
mistakes.
Eventually only the practice (who's picture allow to create
effective predictable code) is the way to check a theory.
Click to expand...

But you don't write effective predictable computer code. You write a
chaotic mush half thought-out reasoning and pure voodoo. The last piece
of 'full working' code you posted to this group earned the epithet "the
most bizarre and obtuse storage method I've ever witnessed", with good
reason, and demonstrated a basic lack of understanding of standard
language constructs.
A theory in contradiction with the practical experience
is worthless IMHO.
Click to expand...

A theory that is contradicted by reality is false, but it takes some
familiarity with testing and analysis methodologies to identify a real
contradiction. That perverse personal mental process that you like to
label 'logic' seems to significantly restrict your ability to create and
apply tests, or analyse the results. A fact that should have been
sufficiently flagged when you posted earlier in the week that your had
spent two months testing Mozilla browsers and concluded that they did
not support - document.styleSheets -, when they have done so since their
beta versions at least.

The notions that originate in your head are also theories, and the
'practical' results you achieve with them are so self evidently inferior
to what can demonstrably be achieved that even you should be questioning
them, and not at all surprised that nobody else gives you any credence
at all.

Richard.
 
V

VK

Richard said:
The javascript array has no potential to have multiple dimensions and so
no potential to be 'jagged'. Both concepts can be successfully
implemented/emulated with javascript but that can not be done with a
single javascript Array, and so the terms 'multi-dimensional' and
'jagged' are not applicable as characteristics of a javascript Array.
Click to expand...

It's too late and I'm too tired to continue this discussion right now.
But I bookmark this statement till the next array question - where
you'll have an opportunity to answer it without using words "dimension"
or "jagged" or "pseudo-dimension" (because pseudo-dimension directly
leads to "jagged"). From my humble and very possibly wrong point of
view it will be funny.
 
T

Thomas 'PointedEars' Lahn

VK said:
JavaScript array is Dinamic, is Sparse and is Jagged.
Click to expand...

Whatever this means to you.
[...]
<http://www.geocities.com/schools_ring/ArrayAndHash.html> is the only
one known (to me at least) resource there all three features along with
other information would be named and illustrated properly: [...]
Click to expand...

That you do not understand the correct terms used in public specifications
and vendors' documentation does not mean that they are bad. That you do
not understand what was written before does not make your explanations,
based on your misconceptions, any better than it.

<URL:http://developer.mozilla.org/js/specs/ecma-262#a-15.4>
<URL:http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Literals#Array_Literals>
<URL:http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Predefined_Core_Objects:Array_Object>
<URL:http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference:Global_Objects:Array>
<URL:http://msdn.microsoft.com/library/en-us/script56/html/08e5f552-0797-4b48-8164-609582fc18c9.asp>
<URL:http://msdn.microsoft.com/library/en-us/jscript7/html/jsobjarray.asp>


PointedEars
 

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