Algorithm to search through and delete repeats in array

In this situation, you normally can't use a for loop for your inner loop. while works well, though:

for(var j = 0; j < $scope.groceryList.length; j++){
    var k = j+1;
    while(k < $scope.groceryList.length){ // each of elements below current element (j)
        if ( $scope.groceryList[j].name == $scope.groceryList[k].name){
            $scope.groceryList.splice(k, 1);
            }
        else {
            ++k;
            }
        }
}

If you splice, don't increment k. If you don't, do.

(I hope I got your indentation right, it's not a style I'm used to.)

I would just sort it and then compare like so....

var arr = ["Apples","Oranges","Oranges","Grapes","Apples"];
 var sorted_arr = arr.sort(); 

  var results = [];
  for (var i = 0; i < arr.length - 1; i++) {
    if (sorted_arr[i + 1] == sorted_arr[i]) {
    results.push(sorted_arr[i]);
  }
 }

alert(results);

Just do an existence check with an associative array:

var exists = {}, i;
for (i = 0; i < arr.length; i += 1) {
    if (exists[arr[i]]) {
        arr.splice(i, 1);
        i--;
    } else {
        exists[arr[i]] = true;
    }
}
// arr should now have no dupes

Underscore.js is the tool I would recommend for doing all your array handling in JavaScript (and also, for, just, like, everything. It is awesome.)

It just so happens that its uniq method will do exactly what you need.

var myArray = ["Apples","Oranges","Oranges","Grapes","Apples"];
_.uniq(myArray);
//returns ["Apples","Oranges","Grapes"]

This code is the simplest solution but requires double the amount of memory--not a problem for the small dataset in your example.

Array.prototype.filterDuplicates = function () {
    var filtered = [];
    for (var i = 0; i < this.length; i++)
        if (filtered.indexOf(this[i]) == -1)
            filtered.push(this[i]);
    return filtered;
}

my favorite way is to use array methods to save code:

arr1=[
    "Apples",
    "Apples",
    "Oranges",
    "Oranges",
    "Oranges",
    "Bananas"
];


var unq= arr1.filter(function unq(a,b,c){return c.indexOf(a)===b;});

alert(unq); // shows "Apples,Oranges,Bananas"

no vars, no artifacts, just logic and results.

EDIT: changed to use only one repetitive array. if you want to filter one array from another, just change "c.indexOf" above to the array's var name.

i prefer to break out the unq function so i can call .filter(unq) from anywhere to get a unique array...

Linear time, constant space algorithm:

1. Have 2 indices (one fast and one slow), both starting from zero
2. Increment both until the previous element is the same as the current one
3. Increment the fast one until you find an element that's different
4. Set the element at the slow index to the element at the fast index
5. Increment both
6. Increment the fast one until it's different from the replacing element
7. Repeat from 4 until the fast one reaches the end.
8. Shorten the list up to the short one

No, I can't give you the JavaScript.

Example:

Input:

Ingredients, Apples, Apples, Oranges, Oranges, Oranges, Bananas

Have 2 indices (one fast and one slow), both starting from zero

   fast
   slow
     V
Ingredients, Apples, Apples, Oranges, Oranges, Oranges, Bananas

Increment both until we the previous element is the same as the current one.

                     fast
                     slow
                       V
Ingredients, Apples, Apples, Oranges, Oranges, Oranges, Bananas

Increment fast until it's different.

                     slow     fast
                       V        V
Ingredients, Apples, Apples, Oranges, Oranges, Oranges, Bananas

Set element at slow to element at fast.

                     slow      fast
                       V         V
Ingredients, Apples, Oranges, Oranges, Oranges, Oranges, Bananas

Increment both.

                               slow     fast
                                 V        V
Ingredients, Apples, Oranges, Oranges, Oranges, Oranges, Bananas

Increment the fast one until it's different from the replacing element (Oranges)

                               slow                       fast
                                 V                          V
Ingredients, Apples, Oranges, Oranges, Oranges, Oranges, Bananas

Set element at slow to element at fast.

                               slow                       fast
                                 V                          V
Ingredients, Apples, Oranges, Bananas, Oranges, Oranges, Bananas

Increment both.

                                        slow                  fast
                                          V                     V
Ingredients, Apples, Oranges, Bananas, Oranges, Oranges, Bananas

Reached the end.

Shorten the list up to slow.

Ingredients, Apples, Oranges, Bananas

http://jsfiddle.net/XYsUm/

var ingredients = [
    "Apples",
    "Apples",
    "Oranges",
    "Oranges",
    "Oranges",
    "Bananas"
];

var uniqIngredients = {};

for (i in ingredients) {
    uniqIngredients[ingredients[i]] = true;
}

ingredients = [];

for (i in uniqIngredients) {
    ingredients.push(i);
}