How to sum of array object in Javascipt

Question

i have this array:

    var res =
[
  { '5': 0 },  { '23': 0 },
  { '74': 0 }, { '45': 0 },
  { '10': 0 }, { '46': 1 },
  { '33': 0 }, { '18': 0 },
  { '67': 1 }, { '28': 0 },
  { '68': 0 }, { '56': 0 },
  { '78': 0 }, { '71': 0 },
  { '50': 1 }, { '14': 0 },
  { '39': 0 }, { '91': 0 },
  { '37': 0 }, { '34': 0 }
];

I want to sum second values to get result. like in this example result must be 2. I am using nodejs, if it helps.

Thank you.

I would probably first go back to the code that generated this data and put it in a more convenient way to process. An object with unknown keys is usually a sign that there's a better way to store and therefore process this data. — jfriend00
– jfriend00, Commented Dec 24, 2020 at 22:15
And, what should your sum do if an object has more than one property in it? — jfriend00
– jfriend00, Commented Dec 24, 2020 at 22:16
As a hint Object.values(obj)[0] will get you the "first" value in an object where "first" is in quotes because if there's more than one value, it's not clear what your algorithm wants to do. — jfriend00
– jfriend00, Commented Dec 24, 2020 at 22:17

Mureinik · Accepted Answer · 2020-12-24 22:27:00Z

1

You could use Object.values to extract the value for each such object and then sum them. Using map and reduce, this can even be done in a one liner:

const total =  res.map(o => Object.values(o)[0]).reduce((a, b) => a + b, 0);

edited Dec 24, 2020 at 22:27

answered Dec 24, 2020 at 22:16

Mureinik

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1 Comment

Mureinik Over a year ago

@Corvus actually, the conversion to number is redundant - I didn't notice you already had number literals there. I've edited my answer to remove it.

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