comparing two hashes

[Jeff Thies]

I need to check if two hashes are identical.

My thoughts are something like this:

function compareHash(has h1,hash2){

if(hash1.length != hash2.length){r eturn false}

for(var key in hash1){
if(hash1[key] != hash2[key]) return false;
}
return true;
}

Have I missed something, or is there a more direct approach?

Jeff

[Lasse Reichstein Nielsen]

Re: comparing two hashes

"Jeff Thies" <nospam@nospam. net> writes:
[color=blue]
> I need to check if two hashes are identical.[/color]

What is a hash?

My guess is that it is an array that you use to store values in. You
use it as a hash *table* (and you should just use a plain object, not
an array).
[color=blue]
> My thoughts are something like this:
>
> function compareHash(has h1,hash2){
>
> if(hash1.length != hash2.length){r eturn false}[/color]

Not really interesting if you have an array. Not interesting at all if
you don't.
[color=blue]
> for(var key in hash1){
> if(hash1[key] != hash2[key]) return false;[/color]

You should compare with !== instead. Otherwise this comparison of two
clearly different objects gives true:
compareHash({ke y:0},{key:false })
[color=blue]
> Have I missed something, or is there a more direct approach?[/color]

Use objects for hash tables, drop the length comparison, and use !==.

/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.'

[Jeff Thies]

Re: comparing two hashes

> > I need to check if two hashes are identical.[color=blue]
>
> What is a hash?[/color]

I don't know what it's called in javascript

var hash={'item1': 'value1' , 'item2': 'value2'}

or

var HASH =new Array();

HASH['some_key']='some_value';


[color=blue]
> My guess is that it is an array that you use to store values in. You
> use it as a hash *table* (and you should just use a plain object, not
> an array).[/color]

Good advice. What I'm trying to do is save this to a temp cookie.

something like:

var hash={'item1' :value1','item2 ': 'value2'}

document.cookie ="my_cookie=[" + escape(hash) + "],["+ escape(hash2) + ..;

I won't always no what the "keys" are so it seemed a good idea to send
them along.

[color=blue]
>[color=green]
> > My thoughts are something like this:
> >
> > function compareHash(has h1,hash2){
> >
> > if(hash1.length != hash2.length){r eturn false}[/color]
>
> Not really interesting if you have an array. Not interesting at all if
> you don't.
>[color=green]
> > for(var key in hash1){
> > if(hash1[key] != hash2[key]) return false;[/color]
>
> You should compare with !== instead.[/color]

an object comparison? Didn't know that! Seems like hash1[key] is a variable
that could be compared that way.
[color=blue]
> Otherwise this comparison of two
> clearly different objects gives true:
> compareHash({ke y:0},{key:false })[/color]

Duh! slaps head.
[color=blue][color=green]
> > Have I missed something, or is there a more direct approach?[/color]
>
> Use objects for hash tables, drop the length comparison, and use !==.[/color]

Will do.

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