Objects in an array with reduce

Question

Why console.log's value always NaN

https://code.sololearn.com/Ws3C0N7dOdsa/?ref=app

Answer 1

If you use reduce without intialValue (second parameter), reduce would take the first element of the array as initialValue of accumulator, which is
{
nama:"Bambang",
kelas:"12 RPL 1",
nilai:50
}

So the the output would be Not a Number (NaN).

If you want to calculate sum of object nilai, you should set initialValue to zero.

angka = aObj.reduce((now,than)=> now + than["nilai"], 0);