push to JSON Array if Object does not exist

Question

I have a JSON as shown below

[
  {
    "name": "Mike",
    "incentives": "23.45",
    "id": "1"
  },
  {
    "name": "Larsen",
    "incentives": "34.78",
    "id": "2"
  },
  {
    "name": "Steve",
    "incentives": "26.78",
    "id": "3"
  }
]

I need to push a new JSON Object into the JSON array if id not exists inside the JSON Object

tried as this way and working , any better way of doing this

$(document).ready(function() {

var idsarray = [];

  var test = [
  {
    "name": "Mike",
    "incentives": "23.45",
    "id": "1"
  },
  {
    "name": "Larsen",
    "incentives": "34.78",
    "id": "2"
  },
  {
    "name": "Steve",
    "incentives": "26.78",
    "id": "3"
  }
];

for(var i=0;i<test.length;i++)
{
idsarray.push(test[i].id)
}

var newobj =  {
    "name": "RAM",
    "incentives": "56.78",
    "id": "4"
  }

  var newid = newobj.id;

if(jQuery.inArray(newid, idsarray) !== -1)
{
test.push(newobj)
}

alert(test.length)

});

your logic is fair enough. only thing is you need to update idsarray with new element added — Bhushan Kawadkar
– Bhushan Kawadkar, Commented Aug 20, 2018 at 11:03

Ankit Agarwal · Accepted Answer · 2018-08-20 11:10:24Z

Your condition is incorrect. It should be jQuery.inArray(newid, idsarray) === -1 because the operation jQuery.inArray(newid, idsarray) will return -1 if the newid is not present in idsarray. So, that is what you need, to check unique occurrence in idsarray.

You can also use the indexOf() operation for the same. idsarray.indexOf(newid) === -1.

OP's code

$(document).ready(function() {

  var idsarray = [];
  var test = [{
      "name": "Mike",
      "incentives": "23.45",
      "id": "1"
    },
    {
      "name": "Larsen",
      "incentives": "34.78",
      "id": "2"
    },
    {
      "name": "Steve",
      "incentives": "26.78",
      "id": "3"
    }
  ];

  for (var i = 0; i < test.length; i++) {
    idsarray.push(test[i].id)
  }

  var newobj = {
    "name": "RAM",
    "incentives": "56.78",
    "id": "4"
  }

  var newid = newobj.id;
  if (jQuery.inArray(newid, idsarray) === -1) {
    test.push(newobj)
  }
  alert(test.length)

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

USING indexOf()

$(document).ready(function() {

  var idsarray = [];
  var test = [{
      "name": "Mike",
      "incentives": "23.45",
      "id": "1"
    },
    {
      "name": "Larsen",
      "incentives": "34.78",
      "id": "2"
    },
    {
      "name": "Steve",
      "incentives": "26.78",
      "id": "3"
    }
  ];

  for (var i = 0; i < test.length; i++) {
    idsarray.push(test[i].id)
  }

  var newobj = {
    "name": "RAM",
    "incentives": "56.78",
    "id": "4"
  }

  var newid = newobj.id;
  if (idsarray.indexOf(newobj) === -1) {
    test.push(newobj)
  }
  alert(test.length)

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Amadan · Accepted Answer · 2018-08-20 11:09:28Z

1

inArray is slow. If you do this once, it's not the worst thing ever, but find or some on the original array would be better:

if (!test.some(o => o.id == newid)) {
  test.push(newobj)
}

However, if you do this often, a much better idea is to make a set, as checking membership in a set is very very fast:

let idset = new Set();
...
if (!idset.has(newid)) {
  test.push(newobj);
  idset.add(newid);
}

You could also use Map (or even plain old object) to combine the two:

let test = new Map();
...
if (!test.has(newid)) {
    test.set(newobj);
}

You can get the array from the Map using test.values().

answered Aug 20, 2018 at 11:09

Amadan

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Comments

Nikhil Aggarwal · Accepted Answer · 2018-08-20 11:45:00Z

You can avoid the use of another array that contains the id of objects. You can use native function Array.some to check for existence and push accordingly.

var test = [{"name":"Mike","incentives":"23.45","id":"1"},{"name":"Larsen","incentives":"34.78","id":"2"},{"name":"Steve","incentives":"26.78","id":"3"}];
var newobj = {"name":"RAM","incentives":"56.78","id":"4"};
if(!test.some(({id}) => id == newobj.id)) test.push(newobj);
console.log(test);

Also, if your push operation is going to be quite frequent then looping every time will affect the performance. Instead of array of ids, you can maintain an map or set of ids as the complexity of search will be O(1).

var test = [{"name":"Mike","incentives":"23.45","id":"1"},{"name":"Larsen","incentives":"34.78","id":"2"},{"name":"Steve","incentives":"26.78","id":"3"}];
var newobj = {"name":"RAM","incentives":"56.78","id":"4"};
var ids = test.reduce((a, {id}) => Object.assign(a, {[id]:id}), {});
if(!ids[newobj.id]) {
   test.push(newobj);
   ids[newobj.id] = newobj.id;
}
console.log(test);

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