Rails spinoffs - Aug 2007 - Creating Hashes

I''m using an object to represent some data, and I have an array of
those objects. I need to determine if an object exists in the array
with a given identifier.

My object looks something like this:

var obj = {
  id: 123,
  val1: "hello",
  val2: "world"
}

There are between 40-100 instances of obj in an Array. I need to know
if the array contains an object such that obj.id = 456.

I''ve looked at the Enumerable.collect() function, but since I need to
compare a large number of items against the array, I''m looking at n*x
run time.

I''m considering converting the Array to a Hash so I can test
"myHash[123]" to see if object 123 is in there. So I need a way to
convert the Array to an Hash such that the Hash''s member keys are the
id property of each object as a value.

This might be my array:
[ {id: 10, val1: "hello world"},
  {id: 22, val1: "hello world"},
  {id: 16, val1: "hello world"},
  {id: 87, val1: "hello world"} ]

And this is what I''d like to have as a Hash:

{  10: {id: 10, val1: "hello world"},
   22: {id: 22, val1: "hello world"},
   16: {id: 16, val1: "hello world"},
   87: {id: 87, val1: "hello world"}  }


So far the best I''ve come up with is a collect iterator on the array
that builds a JSON string of each item. I then pass the
string.evalJSON() to the $H() operator.

Any better suggestions?


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jarrod wrote:
> So far the best I''ve come up with is a collect iterator on the
array
> that builds a JSON string of each item. I then pass the
> string.evalJSON() to the $H() operator.
Ouch! That sounds like a really bad idea. Did you try something like this:

myhash = {};
$A(myarray).each(function(item) {
  myhash[item.id] = item;
})

-- 
Michael Peters
Developer
Plus Three, LP


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On Aug 15, 2007, at 2:05 PM, jarrod wrote:
> So far the best I''ve come up with is a collect iterator on the
array
> that builds a JSON string of each item. I then pass the
> string.evalJSON() to the $H() operator.
>
> Any better suggestions?
If that''s really the way you want to go, why bother with the string- 
 >hash conversion?

var h = {};
arr.each(function (a) {
     h[a.id] = a;
});

console.log( $H(h).inspect() );





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