Find duplicate object in array and mark these [Javascript lodash]

Question

I have an array with objects:

var test = [
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "Some one else home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home1",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  }
];

I would like to mark the objects that they are duplicates, like this (notice the extra property, isDuplicate):

var test = [
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "Some one else home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity",
    isDuplicate: true
  },
	{
  	type: "home1",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity",
    isDuplicate: true
  }
];

If one of the above values change (type, name, country, postalZone or cityName), the object is unique.

I have tried the following for testing purpose. Getting only the unique objects for "type", does not work for me e.g.

_.uniq(test, "type");

Still getting all the array objects. Ofcourse I want to check on more object keys, not only on type, but on all object keys (type, name, country, postalZone or cityName).

The native array function "some", stops if it finds the first duplicate, for me it should not stop...

How can I achieve this?

I have Lodash v4.13.1.

Nenad Vracar · Accepted Answer · 2016-09-16 11:31:40Z

Here is one solution with map() to change object if its found as duplicate and for finding duplicates i used find() and isEqual(). So if duplicate is found it will add property if not it will just return object.

var test = [{
  type: "home",
  name: "My home",
  country: "DE",
  postalZone: "1234",
  cityName: "GermanCity"
}, {
  type: "home",
  name: "Some one else home",
  country: "DE",
  postalZone: "1234",
  cityName: "GermanCity"
}, {
  type: "home",
  name: "My home",
  country: "DE",
  postalZone: "1234",
  cityName: "GermanCity"
}, {
  type: "home1",
  name: "My home",
  country: "DE",
  postalZone: "1234",
  cityName: "GermanCity"
}, {
  type: "home",
  name: "My home",
  country: "DE",
  postalZone: "1234",
  cityName: "GermanCity"
}];


var result = _.map(test, function(o, i) {
  var eq = _.find(test, function(e, ind) {
    if (i > ind) {
      return _.isEqual(e, o);
    }
  })
  if (eq) {
    o.isDuplicate = true;
    return o;
  } else {
    return o;
  }
})

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

Redu · Accepted Answer · 2016-09-16 14:56:11Z

No need for lodash actually. By an invention of Object.prototype.compare() and with pure JS you might do this as follows;

Object.prototype.compare = function(o){
  var ok = Object.keys(this);
  return typeof o === "object" && ok.length === Object.keys(o).length ? ok.every(k => this[k] === o[k]) : false;
};

var myList = [
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "Some one else home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home1",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  },
	{
  	type: "home",
    name: "My home",
    country: "DE",
    postalZone: "1234",
    cityName: "GermanCity"
  }
],
markedList = myList.reduce((p,c) => p.some(o => o.compare(c)) ? (c.isDuplicate = true, p.concat(c))
                                                              : p.concat(c),[]);
console.log(JSON.stringify(markedList,null,4));

You might of course prefer to convert Object.prototype.compare() to a proper function and adapt the code accordingly.

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