Javascript：在数组中搜索重复项

Question

This is what I am trying to do: I present the user with a textarea and he must enter some domains, if he enters the same domain twice (a duplicate) I want to delete the dupes.

So far I have come till the part where I can find the dupes, this is the code I am using:

function check_if_already_in_the_list___manual_textbox()
{

var therows=0;
var thetext = document.forms[0].text.value;
var newtext = thetext.split("\n");
therows+=newtext.length;
var i;
var match_counter=0;

    for(i=0;i<newtext.length;i++) // first iterate over the number of items
    {
        for(j=0;j<newtext.length;j++) // second, start a second loop to compare each other
        {

            if(newtext[j].toLowerCase()==newtext[i].toLowerCase())
            {           
            match_counter++;
            }

        if(match_counter >=2) // Found dupe!
        {alert("Matched:"+newtext[j]+" "+newtext[i]+" Counter"+match_counter);
match_counter=0;}


        }
        alert("Match counter:"+match_counter+ " D:"+newtext[i]);'
match_counter=0;
    }
//alert(""+match_counter);
return match_counter;
}

Any suggestions to do this better would be most appreciated, also I have no idea how to take out the dupes :(
Googling I see that I probably have to use "splice" but not really sure.

Thanks in advance!
R

(PS Sorry the format looks weird, but that happened when I pasted in the code)

Answer 1

Here's my feeble attempt at it. It's similar to

var arr = ["1","2","3","4","5","3","2","3","4"];
var arrCopy = [];
var list = {};

for (var i = 0, len = arr.length; i < len; i++) {
    if(!list[arr[i]])
        arrCopy.push(arr[i]);
    list[arr[i]] = ++list[arr[i]] | 0;
}

The object will also contain how many duplicates there were for each one. arrCopy has the unique values.

EDIT: see RobG's comment concerning hasOwnProperty . In this case it should be

...
    if(!list.hasOwnProperty(arr[i]))
...

Answer 2

Lots of answers. Here's one that uses a generic funciton to create an array of unique members. Note that the result will be sorted, using an object and getting back properties using for..in isn't guaranteed to maintain any particular order.

var el = document.forms[0].text;
el.value = unique(el.value.toLowerCase().split(/[\n\r]/)).join('\n');

function unique(arr) {
  arr.sort();
  var i = arr.length;

  while (i--) {
    if (arr[i] == arr[i - 1]) {
       arr.splice(i, 1);
    }
  }
  return arr;
}

Answer 3

You can make use of something called as associative arrays to solve this problem. See if it works for you.

var initial_array = ['www.yahoo.com', 'www.google.com', 'www.facebook.com', 'www.google.com'];
var set = {};
for (var domain in initial_array){
    set[initial_array[domain].toLowerCase()] = true;
}
alert(set);

Answer 4

1st Copy array, and lowercase it first

2nd Array has a "sort" function in javascript, I suggest you sort it before compare

3rd I saw you are using bubble sorting, it's good. At for(j=0;j<newtext.length;j++) , you do not need to start from 0, you can start from i

last, use something already there, http://api.jquery.com/jQuery.unique/

Answer 5

I think there is a mistake here..

for(i=0;i<newtext.length;i++) // first iterate over the number of items
{
    for(j=0;j<newtext.length;j++) // second, start a second loop to compare each other

This code should not be??

for(i=0;i<newtext.length -1;i++) // first iterate over the number of items
{
    for(j=i+1;j<newtext.length;j++) // second, start a second loop to compare each other

note j=i+1 and newtext.length -1 (this last one is optional)

Then:

  if(newtext[j].toLowerCase()==newtext[i].toLowerCase())
      return 'dupe';