Javascript remove row from multidimensional array when elements are duplicated

Question

I have the following array.

[{
  'firstname': 'John',
  'surname': 'Smith',
  'HouseNo': 'firtree farm'
}, {
  'firstname': 'Paul',
  'surname': 'Smith',
  'HouseNo': 'firtree farm'
}, {
  'firstname': 'John',
  'surname': 'Smith',
  'HouseNo': 'firtreefarm'
}, {
  'firstname': 'John',
  'surname': 'Smith',
  'HouseNo': 'firtree farmhouse'
}, {
  'firstname': 'Paul',
  'surname': 'Smith',
  'HouseNo': 'firtree farmhouse'
}, {
  'firstname': 'Paul',
  'surname': 'Smith',
  'HouseNo': 'FirTree farmhouse'
}]

I need to produce another array that contains no duplicates of element 'HouseNo' and just the element 'HouseNo. Also it need to be case insensitive.

ie.

[{
  'HouseNo': 'firtree farm'
}, {
  'HouseNo': 'firtreefarm'
}, {
  'HouseNo': 'firtree farmhouse'
}, {
  'HouseNo': 'FirTree farmhouse'
}]

The application is a returned set of address's based on a postcode search. I can then offer a filtered list of unique houseNo's they can choose form.

MrWarby

Answer 1

You can keep track of the already seen items in an object, and if you get an item which is not there in the seen , then push it to the result .

var seen = {};
var result = data.reduce(function(result, current) {
    if (!seen[current.HouseNo]) {
        seen[current.HouseNo] = true;
        result.push(current.HouseNo);
    }
    return result;
}, []);
console.log(result);

Output

[ 'firtree farm',
  'firtreefarm',
  'firtree farmhouse',
  'FirTree farmhouse' ]

If you want to maintain the object structure, then while pushing to the result, just create an object like this

result.push({HouseNo: current.HouseNo});

and the result would be

[ { HouseNo: 'firtree farm' },
  { HouseNo: 'firtreefarm' },
  { HouseNo: 'firtree farmhouse' },
  { HouseNo: 'FirTree farmhouse' } ]

If the Order of the data doesn't matter, then you can simply keep adding the HouseNo to an object and finally get the keys like this

var result = data.reduce(function(result, current) {
    result[current.HouseNo] = true;
    return result;
}, {});
console.log(Object.keys(result));