How to add a new object (key-value pair) to an array in javascript?

Question

I have an array as :

items=[{'id':1},{'id':2},{'id':3},{'id':4}];

How should I add a new pair {'id':5} to the array?

Answer 1

Use .push:

items.push({'id':5}); 

Answer 2

.push() will add elements to the end of an array.

Use .unshift() if need to add some element to the beginning of array i.e:

items.unshift({'id':5}); 

Demo:

items = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}];  items.unshift({'id': 0});  console.log(items);

And use .splice() in case you want to add object at a particular index i.e:

items.splice(2, 0, {'id':5});            // ^ Given object will be placed at index 2... 

Demo:

items = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}];  items.splice(2, 0, {'id': 2.5});  console.log(items);

Answer 3

Sometimes .concat() is better than .push() since .concat() returns the new array whereas .push() returns the length of the array.

Therefore, if you are setting a variable equal to the result, use .concat().

items = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}];
newArray = items.push({'id':5})

In this case, newArray will return 5 (the length of the array).

newArray = items.concat({'id': 5})

However, here newArray will return [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}, {'id': 5}].

Answer 4

New solution with ES6

Default object

object = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}];

Another object

object =  {'id': 5};

Object assign ES6

resultObject = {...obj, ...newobj};

Result

[{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}, {'id': 5}];