2

I have a javascript array object:

var items = [
               {address: 'abc'}, {address: 'abc'}, {address: 'abc'}, 
               {address: 'abc'}, {address: 'wer'}, {address: 'xyz'}, 
               {address: 'xyz'}, {address: 'xyz'}
            ];

What I want to do is that I consider 2 items as one item.. If the address of items repeats twice.. i consider it as one item.. the single unique item will be treated as one...

I want its output like this:

[
   {address: 'abc'}, {address: 'abc'}, 
   {address: 'wer'}, 
   {address: 'xyz'}, {address: 'xyz'}
];

Above is the expected output..

The concept is like this:

abc , abc , abc SHOULD BE abc, abc
xyz , xyz, xyz SHOULD BE xyz, xyz
wer SHOULD BE wer

Well what I have tried so far is:

var items = [
           {address: 'abc'}, {address: 'abc'}, {address: 'abc'}, 
           {address: 'abc'}, {address: 'wer'}, {address: 'xyz'}, 
           {address: 'xyz'}, {address: 'xyz'}
        ];
  var itemsNew = [];
  var preItem  = '';
  var a        = 1;
  var x        = false;

  for(var i = 0; i < items.length; i++){

    var itemDeliveryAddress = items[i].address;

    if(a == 2){

      if(preItem == itemDeliveryAddress){

        preItem = '';
        a=1;
      }
      else {

        preItem = '';
        a=1;
        itemsNew.push(itemDeliveryAddress);
      }
    }
    else {

      a++;
      preItem = itemDeliveryAddress;
      itemsNew.push(itemDeliveryAddress);    
    }
  }

But the above code is not grouping the items properly.. I am getting this output:

abc,abc,wer,xyz,xyz

Note: I have sorted the array first in ascending order

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2
  • In your expected output you use JSON format, and you group by inserting newlines. Is that literally the output you want? Or are you describing an object that you want to have? Note that you are not grouping anything, not even in that object. It is just an array with 5 elements. The fact that you add newlines after commas does not bring any change to such an object. Commented Jun 28, 2016 at 14:35
  • I expected output in JSON format Commented Jun 28, 2016 at 15:11

2 Answers 2

Reset to default
4

You could filter it with a counter and Array#filter.

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

This proposal uses the thisArg, a really empty object as this object inside of the callback.

Basically this[a.address] is the counter, which is if not exist, initialised with zero and then incremented by one.

After counting, the counter is used for the return. If the value is odd, the item is included in the result set.

While this is persistent in all callbacks, there is no need for sorting, because the counter need no specific order.

var items = [{ address: 'abc' }, { address: 'abc' }, { address: 'abc' }, { address: 'abc' }, { address: 'wer' }, { address: 'xyz' }, { address: 'xyz' }, { address: 'xyz' }],
    result = items.filter(function (a) {
        this[a.address] = (this[a.address] || 0) + 1;
        return this[a.address] % 2;
    }, Object.create(null));

console.log(result);

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4 Comments

Can you explain this code I bit.. I want to understand each step of your code. Also do I need to sort the array first ?
Your code is not working fine against this array:::: var items = [ { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' } ]; There should be 3 Taxila
you get only 2. should there be 3? and why?
Because that is the case. If there are total 4 same addresses.. than it should return 2 address instead of 4.. if there are 5 same address than it should return total 3 address, because we got 2 from 4 same addresses, so the 5th one is remaining, we have to consider the fifth one as well
1

You can use array.splice to modify the array inplace.

//Initialize array (sorted)
var items = [{ address: 'abc' }, { address: 'abc' }, { address: 'abc' }, { address: 'abc' }, { address: 'wer' }, { address: 'xyz' }, { address: 'xyz' }, { address: 'xyz' }];
var groupedProperty = "address";   //Modify this string to change which property to group by
//Iterate through sorted array
for( var i = 1; i < items.length; i++ )  //Iterate, start with the 2nd (since we refer to `i - 1`) item
    if( items[i][groupedProperty] == items[i-1][groupedProperty] )  //Check if current item's prop matches previous item's prop
      items.splice(i, 1);                //Remove current item inplace, since there is a match. Other items (> i) shifted back automatically

console.log(items);

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8 Comments

What's nice is that with splice, and wanting to keep one of every pair of objects, the indicies just line up perfectly so no mangling of i is needed. :D
Can you explain this code I bit.. I want to understand each step of your code. Also do I need to sort the array first ?
@HassanSardar. Done
Your code isnt working fine against this array: var items = [ { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Airport Rd' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Lahore' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' }, { deliveryAddress: 'Taxila' } ];
Did you modify the code such that items[i].address == items[i-1].address is now items[i].deliveryAddress == items[i-1].deliveryAddress?
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