Forum: Rails Spinoffs (closed, excessive spam) Finding a duplicate value in an array

I am trying to detect whenever an array has a duplicate value and then
produce an alert to the user that a dupe exists with the value of the
dupe.

Reading 'Prototype & Scriptaculous IN ACTION', I have been able to
begin the coding to obtain the textarea values and sort the resultant
array.  I am having trouble coding the duplicate value detection.

Here is my limited code:
var txtarea = $F('txtarea4').split(/[\n\r]+/);
var atxtarea = $A(txtarea).sort();

I think I should use the .detect or .any methods.

Frank

After sorting through the array, just loop through it and see if the
next value equals the current value.

Writing one FOR loop isn't going to kill you :)

If you're in that much of a pinch, there's always:

if (my_array.length == my_array.uniq().length) { ... }

On Mon, Jun 30, 2008 at 8:22 AM, Diodeus <diodeus@gmail.com> wrote:

>
> After sorting through the array, just loop through it and see if the
> next value equals the current value.
>
> Writing one FOR loop isn't going to kill you :)


--
Science answers questions; philosophy questions answers.

It's not complicated at all. Take a look at
http://github.com/kangax/protolicious/tree/master/...

-- kangax

I have tried your suggestion. I am retrieved data from a <textarea>
form element with these values:
1111
2222
3333
1111
4444

My code that I have been testing using Firefox 3 and Firebug 1.0b4 is:
var txtarea = $F('txtarea4').split(/[\n\r]+/);
var atxtarea = $A(txtarea).sort();
Array.prototype.isUnique = function(value) {
  var idx = this.indexOf(value);
  return this.indexOf(value, idx + 1 == -1);
};
for (i=0; i<=atxtarea.length; i++) {
  alert(atxtarea[i]);
  atxtarea.isUnique(atxtarea[i]);
}

The 'alert' shows an 'undefined' value at the end of the loop.  I am
receiving a -1 after the loop.
I have tried to setup the test using:
[1111,2222,3333,1111,4444].isUnique(1111) and get a 0 in return
(assume this is the index value of 1111) and not a -1 as I would
expect.

Can you provide me some additional assistance??

You changed the method, so it doesn't work. The last line should be:

this.indexOf(value, idx + 1) == -1;
...
[1,2,3,1,2].isUnique(1); // false
[1,2,3,1,2].isUnique(3); // true

-- kangax

Just discovered the mistake, but, I get 'true' with the '1111'  value
twice in the list or once in the list.

Frank

FYI,
Here is the code that I finally ended up with:
function chkdupes() {
var txtarea = $F('txtarea4').split(/[\n\r]+/);
var atxtarea = $A(txtarea).sort();
 for (i=0; i<=atxtarea.length-1; i++) {
  var idx = i+1;
  if (atxtarea[i] ==  atxtarea[idx]) { alert('Duplicate value = ' +
atxtarea[i]);
   var dupval = atxtarea[i];
   var farea = atxtarea.join('\n');
   $('txtarea4').value = farea;
   $('txtarea4').focus();
  };
 }
}
It works as I intended. I also want to code a set focus on the element
that was reported to be the duplication item.

Frank