How to sum all of values from specific key in object?

Question

Let's say I have a array that contains a multiple object like:

var arr = [{ 'credit': 1, 'trash': null }, { 'credit': 2, 'trash': null}]

I want to get a sum of all credit value from arr array. so expected sum value is 3. so I used this code:

arr.reduce((obj, total) => obj.credit + total)

but when I run this, I get "1[object Object]" which is really weird.

Ps: I'm trying to implement this using ES6 not ES5

Answer 1

Two problems: your total and obj arguments are backwards, and you need to provide something to initialize the total variable (that's the ,0 part)

arr.reduce((total, obj) => obj.credit + total,0)
// 3