How to make ng-repeat filter out duplicate results

I'm running a simple ng-repeat over a JSON file and want to get category names. There are about 100 objects, each belonging to a category - but there are only about 6 categories.

My current code is this:

<select ng-model="orderProp" >
  <option ng-repeat="place in places" value="{{place.category}}">{{place.category}}</option>
</select>

The output is 100 different options, mostly duplicates. How do I use Angular to check whether a {{place.category}} already exists, and not create an option if it's already there?

edit: In my javascript, $scope.places = JSON data, just to clarify

You could use the unique filter from AngularUI (source code available here: AngularUI unique filter) and use it directly in the ng-options (or ng-repeat).

<select ng-model="orderProp" ng-options="place.category for place in places | unique:'category'">
    <option value="0">Default</option>
    // unique options from the categories
</select>

Or you can write your own filter using lodash.

app.filter('unique', function() {
    return function (arr, field) {
        return _.uniq(arr, function(a) { return a[field]; });
    };
});

You can use 'unique'(aliases: uniq) filter in angular.filter module

usage: colection | uniq: 'property'
you can also filter by nested properties: colection | uniq: 'property.nested_property'

What you can do, is something like that..

function MainController ($scope) {
 $scope.orders = [
  { id:1, customer: { name: 'foo', id: 10 } },
  { id:2, customer: { name: 'bar', id: 20 } },
  { id:3, customer: { name: 'foo', id: 10 } },
  { id:4, customer: { name: 'bar', id: 20 } },
  { id:5, customer: { name: 'baz', id: 30 } },
 ];
}

HTML: We filter by customer id, i.e remove duplicate customers

<th>Customer list: </th>
<tr ng-repeat="order in orders | unique: 'customer.id'" >
   <td> {{ order.customer.name }} , {{ order.customer.id }} </td>
</tr>

result
Customer list:
foo 10
bar 20
baz 30

this code works for me.

app.filter('unique', function() {

  return function (arr, field) {
    var o = {}, i, l = arr.length, r = [];
    for(i=0; i<l;i+=1) {
      o[arr[i][field]] = arr[i];
    }
    for(i in o) {
      r.push(o[i]);
    }
    return r;
  };
})

and then

var colors=$filter('unique')(items,"color");

If you want to list categories, I think you should explicitly state your intention in the view.

<select ng-model="orderProp" >
  <option ng-repeat="category in categories"
          value="{{category}}">
    {{category}}
  </option>
</select>

in the controller:

$scope.categories = $scope.places.reduce(function(sum, place) {
  if (sum.indexOf( place.category ) < 0) sum.push( place.category );
  return sum;
}, []);

Here's a straightforward and generic example.

The filter:

sampleApp.filter('unique', function() {

  // Take in the collection and which field
  //   should be unique
  // We assume an array of objects here
  // NOTE: We are skipping any object which
  //   contains a duplicated value for that
  //   particular key.  Make sure this is what
  //   you want!
  return function (arr, targetField) {

    var values = [],
        i, 
        unique,
        l = arr.length, 
        results = [],
        obj;

    // Iterate over all objects in the array
    // and collect all unique values
    for( i = 0; i < arr.length; i++ ) {

      obj = arr[i];

      // check for uniqueness
      unique = true;
      for( v = 0; v < values.length; v++ ){
        if( obj[targetField] == values[v] ){
          unique = false;
        }
      }

      // If this is indeed unique, add its
      //   value to our values and push
      //   it onto the returned array
      if( unique ){
        values.push( obj[targetField] );
        results.push( obj );
      }
     
    }
    return results;
  };
})

The markup:

<div ng-repeat = "item in items | unique:'name'">
  {{ item.name }}
</div>
<script src="your/filters.js"></script>

I decided to extend @thethakuri's answer to allow any depth for the unique member. Here's the code. This is for those who don't want to include the entire AngularUI module just for this functionality. If you're already using AngularUI, ignore this answer:

app.filter('unique', function() {
    return function(collection, primaryKey) { //no need for secondary key
      var output = [], 
          keys = [];
          var splitKeys = primaryKey.split('.'); //split by period
  

      angular.forEach(collection, function(item) {
            var key = {};
            angular.copy(item, key);
            for(var i=0; i<splitKeys.length; i++){
                key = key[splitKeys[i]];    //the beauty of loosely typed js :)
            }

            if(keys.indexOf(key) === -1) {
              keys.push(key);
              output.push(item);
            }
      });

      return output;
    };
});

Example

<div ng-repeat="item in items | unique : 'subitem.subitem.subitem.value'"></div>

UPDATE

I was recomending the use of Set but sorry this doesn't work for ng-repeat, nor Map since ng-repeat only works with array. So ignore this answer. anyways if you need to filter out duplicates one way is as other has said using angular filters, here is the link for it to the getting started section.

---

Old answer

Yo can use the ECMAScript 2015 (ES6) standard Set Data structure, instead of an Array Data Structure this way you filter repeated values when adding to the Set. (Remember sets don't allow repeated values). Really easy to use:

var mySet = new Set();

mySet.add(1);
mySet.add(5);
mySet.add("some text");
var o = {a: 1, b: 2};
mySet.add(o);

mySet.has(1); // true
mySet.has(3); // false, 3 has not been added to the set
mySet.has(5);              // true
mySet.has(Math.sqrt(25));  // true
mySet.has("Some Text".toLowerCase()); // true
mySet.has(o); // true

mySet.size; // 4

mySet.delete(5); // removes 5 from the set
mySet.has(5);    // false, 5 has been removed

mySet.size; // 3, we just removed one value

I had an array of strings, not objects and i used this approach:

ng-repeat="name in names | unique"

with this filter:

angular.module('app').filter('unique', unique);
function unique(){
return function(arry){
        Array.prototype.getUnique = function(){
        var u = {}, a = [];
        for(var i = 0, l = this.length; i < l; ++i){
           if(u.hasOwnProperty(this[i])) {
              continue;
           }
           a.push(this[i]);
           u[this[i]] = 1;
        }
        return a;
    };
    if(arry === undefined || arry.length === 0){
          return '';
    }
    else {
         return arry.getUnique(); 
    }
	
  };
}

It seems everybody is throwing their own version of the unique filter into the ring, so I'll do the same. Critique is very welcome.

angular.module('myFilters', [])
  .filter('unique', function () {
    return function (items, attr) {
      var seen = {};
      return items.filter(function (item) {
        return (angular.isUndefined(attr) || !item.hasOwnProperty(attr))
          ? true
          : seen[item[attr]] = !seen[item[attr]];
      });
    };
  });

Here's a template-only way to do it (it's not maintaining the order, though). Plus, the result will be ordered as well, which is useful in most cases:

<select ng-model="orderProp" >
   <option ng-repeat="place in places | orderBy:'category' as sortedPlaces" data-ng-if="sortedPlaces[$index-1].category != place.category" value="{{place.category}}">
      {{place.category}}
   </option>
</select>

None of the above filters fixed my issue so I had to copy the filter from official github doc. And then use it as explained in the above answers

angular.module('yourAppNameHere').filter('unique', function () {

return function (items, filterOn) {

if (filterOn === false) {
  return items;
}

if ((filterOn || angular.isUndefined(filterOn)) && angular.isArray(items)) {
  var hashCheck = {}, newItems = [];

  var extractValueToCompare = function (item) {
    if (angular.isObject(item) && angular.isString(filterOn)) {
      return item[filterOn];
    } else {
      return item;
    }
  };

  angular.forEach(items, function (item) {
    var valueToCheck, isDuplicate = false;

    for (var i = 0; i < newItems.length; i++) {
      if (angular.equals(extractValueToCompare(newItems[i]), extractValueToCompare(item))) {
        isDuplicate = true;
        break;
      }
    }
    if (!isDuplicate) {
      newItems.push(item);
    }

  });
  items = newItems;
}
return items;
  };

});

If you want to get unique data based on the nested key:

app.filter('unique', function() {
        return function(collection, primaryKey, secondaryKey) { //optional secondary key
          var output = [], 
              keys = [];

          angular.forEach(collection, function(item) {
                var key;
                secondaryKey === undefined ? key = item[primaryKey] : key = item[primaryKey][secondaryKey];

                if(keys.indexOf(key) === -1) {
                  keys.push(key);
                  output.push(item);
                }
          });

          return output;
        };
    });

Call it like this :

<div ng-repeat="notify in notifications | unique: 'firstlevel':'secondlevel'">

Add this filter:

app.filter('unique', function () {
return function ( collection, keyname) {
var output = [],
    keys = []
    found = [];

if (!keyname) {

    angular.forEach(collection, function (row) {
        var is_found = false;
        angular.forEach(found, function (foundRow) {

            if (foundRow == row) {
                is_found = true;                            
            }
        });

        if (is_found) { return; }
        found.push(row);
        output.push(row);

    });
}
else {

    angular.forEach(collection, function (row) {
        var item = row[keyname];
        if (item === null || item === undefined) return;
        if (keys.indexOf(item) === -1) {
            keys.push(item);
            output.push(row);
        }
    });
}

return output;
};
});

Update your markup:

<select ng-model="orderProp" >
   <option ng-repeat="place in places | unique" value="{{place.category}}">{{place.category}}</option>
</select>

This might be overkill, but it works for me.

Array.prototype.contains = function (item, prop) {
var arr = this.valueOf();
if (prop == undefined || prop == null) {
    for (var i = 0; i < arr.length; i++) {
        if (arr[i] == item) {
            return true;
        }
    }
}
else {
    for (var i = 0; i < arr.length; i++) {
        if (arr[i][prop] == item) return true;
    }
}
return false;
}

Array.prototype.distinct = function (prop) {
   var arr = this.valueOf();
   var ret = [];
   for (var i = 0; i < arr.length; i++) {
       if (!ret.contains(arr[i][prop], prop)) {
           ret.push(arr[i]);
       }
   }
   arr = [];
   arr = ret;
   return arr;
}

The distinct function depends on the contains function defined above. It can be called as array.distinct(prop); where prop is the property you want to be distinct.

So you could just say $scope.places.distinct("category");

Create your own array.

<select name="cmpPro" ng-model="test3.Product" ng-options="q for q in productArray track by q">
	<option value="" >Plans</option>
</select>

 productArray =[];
angular.forEach($scope.leadDetail, function(value,key){
    var index = $scope.productArray.indexOf(value.Product);
    if(index === -1)
    {
        $scope.productArray.push(value.Product);
    }
});