How to check if a specific object already exists in an array before adding it

Question

I have this array:

[{"name": "Olvier", "id": 123 }, {"name": "Olvier", "id": 124 }]

Now my goal is to prevent adding the same object again to the array:

{"name": "Olvier", "id": 123 }

Is there a Method to do this?

Answer 1

If your object is created earlier and has the same reference as the one in the array, you can use indexOf:

var myObj = { a: 'b' };
myArray.push(myObj);
var isInArray = myArray.indexOf(myObj) !== -1;

Otherwise you can check it with find:

var isInArray = myArray.find(function(el){ return el.id === '123' }) !== undefined;

Answer 2

If the id's are unique you can simply check if an object with a certain id exists:

const collection = [
    {"name": "Olvier", "id": 123 },
    {"name": "Olvier", "id": 124 }
];

let person = { "name": "Olvier", "id": 123 };

function addPerson(person) {
    const existingIds = collection.map((addedPerson) => addedPerson.id);

    if (! existingIds.includes(person.id)) {
        collection.push(person);
    }
}

addPerson(person);

Answer 3

You could use Array#some method to determinate that item is already in array or not:

var arr = [
  { name: 'Olvier', id: 123 },
  { name: 'Olvier', id: 124 }
];
var existingItem = arr[1];
var newItem = { name: 'John', id: 125 };
    
if (!arr.some(item => item === existingItem)) {
  arr.push(existingItem);
}
console.log(arr);
    
if (!arr.some(item => item === newItem)) {
  arr.push(newItem);
}
console.log(arr);