Unable to push the elements into empty array using concat

Question

I tried using concat but unable to get array like [1,2,66] . By using push I got. But using concat is it possible or what is the reason I am not getting the result.

const arr = [1, 2, 66];
const data = arr.reduce((obj, k) => { 
            obj.concat(k); 
            return obj 
},[]);
console.log(data);

Answer 1

The concat() method is used to merge two or more arrays . This method does not change the existing arrays, but instead returns a new array .

So, obj.concat(k) doesn't do anything, and you're returning an unchanged obj in the next line.

To solve this you can assign the concat to a new variable and return that...

const newObj = obj.concat(k);
return newObj;

... or simply return the result of the concat:

return obj.concat(k);

 const arr = [1, 2, 66]; const data = arr.reduce((obj, k) => { return obj.concat(k); }, []); console.log(data);