CODEWITHSUNDEEP
javascriptangularjsarrays
A1RStack
A1RStack

Reputation: 85

Add attribute to specific objects in an array

In AngularJS/Javascript i have an array of objects, these objects contain a date. I want to order these objects by date and add an attribute to the last object with a specific datetime. So if 2 objects have the same date i want to add the attribute to the one with the latest time. If there is only one object with one date i want to add the attribute to that object.

An example:

input:   var arr = [
          {A: {"Date": "2017-08-14T15:15:00"} B:{}} 
          {A: {"Date": "2017-08-14T16:15:00"} B:{}} //<--- Add attribute to this object 
         ] 

output:  var arr = [
          {A: {"Date": "2017-08-14T15:15:00"} B:{}} 
          {A: {"Date": "2017-08-14T16:15:00"} B:{} C:{"NewAttribute": "true"}} 
         ]

How do i go about programming this? Originally i was thinking about using a for loop to compare all the objects with each other but i have no idea how to implement it.

Upvotes: 0

Views: 561

Answers (2)

Yosvel Quintero
Yosvel Quintero

Reputation: 19070

You can first sort the array by Date using Array.prototype.sort() and than add the new attribute to the last element:

var arr = [
      {A: {"Date": "2017-08-14T15:15:00"},B: {}},
      {A: {"Date": "2017-08-16T16:15:00"},B: {}},
      {A: {"Date": "2017-08-24T16:15:00"},B: {}},
      {A: {"Date": "2017-08-24T16:15:00"},B: {}, C: {}}
    ],
    alphabetArr = 'abcdefghijklmnopqrstuvwxyz'
      .toLocaleUpperCase()
      .split(''),
    lastElementLength = 0;

// Sort the array
arr.sort(function (a, b) {
  return new Date(b.A.date) - new Date(a.A.date);
});

// Get last element properties length
lastElementLength = Object.keys(arr[arr.length - 1]).length;

// Adds new attribute to last element with the proper name..
arr[arr.length - 1][alphabetArr[lastElementLength]] = {
  "NewAttribute": "true"
};

console.log(arr);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 0

PeterMader
PeterMader

Reputation: 7275

I hope I understood what you want:

var arr = [
  {A: {"Date": "2017-08-14T15:15:00"}, B:{}}, // won't get the new property
  {A: {"Date": "2017-08-14T16:12:00"}, B:{}}, // will get the new property
  {A: {"Date": "2017-08-14T15:15:00"}, B:{}}, // will get the new property
  {A: {"Date": "2017-08-14T16:14:00"}, B:{}}, // won't get the new property
  {A: {"Date": "2017-08-14T16:14:00"}, B:{}}  // will get the new property
];

// sort the array by date in descending order
var sorted = arr.sort(({A: { Date: d1 }}, {A: { Date: d2 }}) => new Date(d2).getTime() - new Date(d1).getTime());

// eventually add the new property
sorted.reduce((acc, o) => {
  var date = o.A.Date;
  if (acc !== date) {
    // the date isn't equal to the date of the last item, so it's
    // either the only item with that date
    // or the first (in reversed order) item with that date
    o.C = {"NewAttribute": "true"};
  }
  return date;
}, '');

// reverse the array
var result = sorted.slice().reverse();

console.log(result);

Upvotes: 1

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