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unique reference id


I would like to be able to convert any reference (function, object, or
array) into unique string id and retrieve original reference afterwards
using same id.

The following code does this but only for functions, and for some
unknown reason does not work properly for other kind of references.
var func = function(){};
var ref_id = $GS(func);
// get original reference
var func_2 = $GO(ref_id);
function $GS (ref) { return jsref(ref, "gstr"); }
function $GO (s) { return jsref(s, "gobj"); }
function jsref (ref, what) {

// guess
if (!what) {
what = (typeof(ref) == "string") ? "gobj" : "gstr";
}

var c = jsref;

if (!c.str_ref) c.str_ref = {};
if (!c.ref_str) c.ref_str = {};
if (!c.n) c.n = 0;

if (what == "gstr") {
if (!c.ref_str[ref]) {
c.n++;
c.ref_str[ref] = c.n;
c.str_ref[c.n] = ref;
}
return "jsref:"+ c.ref_str[ref];
}
else if (what == "gobj") {
ref = ref.replace(/\D+/g, '');
return c.str_ref[ref];
}
return null;
}
Oct 14 '08 #1
17 1718
Matija Papec schreef:
I would like to be able to convert any reference (function, object, or
array) into unique string id and retrieve original reference afterwards
using same id.

The following code does this but only for functions, and for some
unknown reason does not work properly for other kind of references.
var func = function(){};
var ref_id = $GS(func);
// get original reference
var func_2 = $GO(ref_id);
function $GS (ref) { return jsref(ref, "gstr"); }
function $GO (s) { return jsref(s, "gobj"); }
function jsref (ref, what) {

// guess
if (!what) {
what = (typeof(ref) == "string") ? "gobj" : "gstr";
}

var c = jsref;

if (!c.str_ref) c.str_ref = {};
if (!c.ref_str) c.ref_str = {};
if (!c.n) c.n = 0;

if (what == "gstr") {
if (!c.ref_str[ref]) {
c.n++;
c.ref_str[ref] = c.n;
c.str_ref[c.n] = ref;
}
return "jsref:"+ c.ref_str[ref];
}
else if (what == "gobj") {
ref = ref.replace(/\D+/g, '');
return c.str_ref[ref];
}
return null;
}
Hi,

Just curious: Why don't you simply store the reference itself?

Regards,
Erwin Moller

--
Oct 14 '08 #2
Erwin Moller wrote:
> }
return null;
}

Hi,

Just curious: Why don't you simply store the reference itself?
The reason is ajax.
When making an ajax call, client side is deciding what reference to pass
to server, so client can later operate on the same reference.

Unfortunately references does not survive ajax calls, so there is a need
for unique string representation of reference.
Oct 14 '08 #3
Matija Papec schreef:
Erwin Moller wrote:
>> }
return null;
}
Hi,

Just curious: Why don't you simply store the reference itself?

The reason is ajax.
When making an ajax call, client side is deciding what reference to pass
to server, so client can later operate on the same reference.

Unfortunately references does not survive ajax calls, so there is a need
for unique string representation of reference.
Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?
Pass the number via Ajax around, and when the server answer, use the
number to look up the reference.

Regards,
Erwin Moller

--
Oct 14 '08 #4
Erwin Moller schreef:
Matija Papec schreef:
>Erwin Moller wrote:
>>> }
return null;
}
Hi,

Just curious: Why don't you simply store the reference itself?

The reason is ajax.
When making an ajax call, client side is deciding what reference to pass
to server, so client can later operate on the same reference.

Unfortunatel y references does not survive ajax calls, so there is a need
for unique string representation of reference.

Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?
That was poorly phrased.
I mean something like this:

var count=0;
var myRefs = new Array();
function getANumberForTh isRef(aRef){
count++;
myRefs[count] = aRef;
}

// do your Ajaxstuff here

function getARefForThisN umber(aNum){
return myRefs[aNum];
}

Regards,
Erwin Moller
Pass the number via Ajax around, and when the server answer, use the
number to look up the reference.

Regards,
Erwin Moller

--
Oct 14 '08 #5
Erwin Moller schreef:
Erwin Moller schreef:
>Matija Papec schreef:
>>Erwin Moller wrote:
}
return null;
}
Hi,

Just curious: Why don't you simply store the reference itself?

The reason is ajax.
When making an ajax call, client side is deciding what reference to pass
to server, so client can later operate on the same reference.

Unfortunate ly references does not survive ajax calls, so there is a need
for unique string representation of reference.

Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?

That was poorly phrased.
I mean something like this:

var count=0;
var myRefs = new Array();
function getANumberForTh isRef(aRef){
count++;
myRefs[count] = aRef;
-- return count;
}
/me gets a coffee....

Regards,
Erwin Moller

>
// do your Ajaxstuff here

function getARefForThisN umber(aNum){
return myRefs[aNum];
}

Regards,
Erwin Moller
>Pass the number via Ajax around, and when the server answer, use the
number to look up the reference.

Regards,
Erwin Moller


--
Oct 14 '08 #6
Erwin Moller wrote:
>>Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?

That was poorly phrased.
I mean something like this:

var count=0;
var myRefs = new Array();
function getANumberForTh isRef(aRef){
count++;
myRefs[count] = aRef;
Yes, I'm already doing this[1], but unfortunately getting same id for
two different objects,
http://www.mcs-informatika.hr/~mcs_matija/js/
[1] I'm also taking care so that the same reference always corresponds
to the same "count" number

>}

/me gets a coffee....
:)

Oct 14 '08 #7
Matija Papec schreef:
Erwin Moller wrote:
>>>Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?
That was poorly phrased.
I mean something like this:

var count=0;
var myRefs = new Array();
function getANumberForTh isRef(aRef){
count++;
myRefs[count] = aRef;

Yes, I'm already doing this[1], but unfortunately getting same id for
two different objects,
http://www.mcs-informatika.hr/~mcs_matija/js/
[1] I'm also taking care so that the same reference always corresponds
to the same "count" number
Hi,

I checked your code and added some comments after //.
<script>

alert($GS( {foo:1} ));
alert($GS( {bar:2} ));
function $GS (ref) { return jsref(ref, "gstr"); }
function $GO (s) { return jsref(s, "gobj"); }
function jsref (ref, what) {

// guess
if (!what) {
what = (typeof(ref) == "string") ? "gobj" : "gstr";
}

// OK, so here you make c pointing to some reference.
var c = jsref;

if (!c.str_ref) c.str_ref = {};
if (!c.ref_str) c.ref_str = {};
if (!c.n) c.n = 0;

if (what == "gstr") {
if (!c.ref_str[ref]) {
// Here you ADD a property to c, so that is a property for each object.
c.n++;

c.ref_str[ref] = c.n;
c.str_ref[c.n] = ref;
}
return "jsref:"+ c.ref_str[ref];
}
else if (what == "gobj") {
ref = ref.replace(/\D+/g, '');
return c.str_ref[ref];
}
return null;
}
</script>
Conclusion: You are NOT doing what I suggested.
You are adding the n property to your object: poluting your objects with
that, and possibly overwriting existing ones (I cannot tell).

Solution: Review my earlier posted code and use that approach. Use 1
counter for all and don't touch the objects the references point to.

Disclaimer:
Possibly I am missing something since I never use $ in Javascript in the
way you do. I only use $ in regular expressions in JavaScript.
I looked it up in my Definitive Guide 4th edition, but it is not listed
in there in the way you use it.
So maybe I miss something important. ;-)

I have no time right now to investigate the $ futher, but hope my
comments help nonetheless

Regards,
Erwin Moller
>
>>}
/me gets a coffee....

:)

--
Oct 15 '08 #8
Matija Papec wrote:
Erwin Moller wrote:
>>>Why don't you make a simple counter (incremental number) and put the
reference as a number in an array or object?
That was poorly phrased.
I mean something like this:

var count=0;
var myRefs = new Array();
function getANumberForTh isRef(aRef){
count++;
myRefs[count] = aRef;

Yes, I'm already doing this[1], but unfortunately getting same id for
two different objects,
That can only be because either you do not test whether you already stored a
reference to the same object, or because there are different objects.
http://www.mcs-informatika.hr/~mcs_matija/js/
q.e.d.

`{x: 1}' and `{x: 1}' (and `[x]' and `[x]') result in references to
*different* objects ({x: 1} != {x: 1}). Each Object (and Array) object
initializer creates a new Object(/Array) object and results in a reference
to it. (In contrast to RegExp object initializers; however, /x/ != /x/ by
definition.)

So what you really want to test is whether two objects have the same
(enumerable) properties and whether those properties have the same value.
One general way to do that:

var equal = true;
for (var p in o1)
{
if (!o2.hasOwnProp erty(p) || o2[p] !== o1[p])
{
equal = false;
break;
}
}

for (var p in o2)
{
if (!o1.hasOwnProp erty(p) || o1[p] !== o2[p])
{
equal = false;
break;
}
}

Object.prototyp e.hasOwnPropert y() requires an implementation of ECMAScript
Ed. 3. You can achieve greater compatibility but less precision with an
alternative to hasOwnProperty( ) and, optionally, also with loose comparison
(`!=').

Also note that this needs to be improved for deep compare, and for inherited
enumerable properties.
PointedEars
--
realism: HTML 4.01 Strict
evangelism: XHTML 1.0 Strict
madness: XHTML 1.1 as application/xhtml+xml
-- Bjoern Hoehrmann
Oct 15 '08 #9
Thomas 'PointedEars' Lahn wrote:
>>> myRefs[count] = aRef;
Yes, I'm already doing this[1], but unfortunately getting same id for
two different objects,

That can only be because either you do not test whether you already stored a
reference to the same object, or because there are different objects.
>http://www.mcs-informatika.hr/~mcs_matija/js/

q.e.d.

`{x: 1}' and `{x: 1}' (and `[x]' and `[x]') result in references to
*different* objects ({x: 1} != {x: 1}).
Yes, of course they refer to different objects and I'm expecting such
behavior.
In the mean time I found what was the problem when looking for object id
in lookup table.
var h1 = {foo: 33};
var h2 = {foo: 33};
// false as expected
alert(h1==h2);
var lookup = {};
lookup[h1] = true;
// true, but I'm expecting false or undefined
alert(lookup[h2]);

It seems that references cannot be used as *object keys* so lookup fails
when searching for reference.

>Each Object (and Array) object
initializer creates a new Object(/Array) object and results in a reference
to it. (In contrast to RegExp object initializers; however, /x/ != /x/ by
definition.)

So what you really want to test is whether two objects have the same
(enumerable) properties and whether those properties have the same value.
One general way to do that:
Yes, that would be solution for comparing object properties.
tnx
Oct 17 '08 #10

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