How to add object within array in javascript?

I have a array object now I want to add another object inside existing array object as given below:-

Output should be like this:- [{​a:1,b:2,c:3,d:4}​]

let a =[{a:1,b:2,c:3}];
let d={d:4}

console.log([...a,d]);

Thanks for your support!

>Solution :

To get the shown output (single object in an array), you can spread (add) d into a[0]

let a = [{a:1,b:2,c:3}];
let d={d:4}
a[0] = { ...a[0], ...d }
console.log(a);

But if you don’t need a dynamic solution, I’d recommend dales way:

a[0]['d'] = 4