Length of Array of Objects in JavaScript

Question

I understand that finding the length of a JS object has been answered extensively here

With one of the suggested solutions being Object.keys(myObj).length

However, I'm struggling to find out how can I find the length of all properties contained on an array of objects.

ie:

const users = [
  {
    firstName: "Bruce",
    lastName: "Wayne",
    id: "1",
  },

  {
    firstName: "Peter",
    lastName: "Parker",
    id: "2"
  },

  {
    firstName: "Tony",
    lastName: "Stark",
    id: "3"
  }
];

Object.keys(users).length //3

Given the example above, How can I output a length of 9 retrieving all the properties on the array of objects?

Could this be done using a reduce method? Thanks in advance.

@DeepikaRao that only gives the length for [1] which is 3 — Null isTrue
– Null isTrue, Commented Dec 15, 2018 at 5:32

Null isTrue · Accepted Answer · 2018-12-15 06:25:29Z

10

Yes, reduce is the appropriate method - on each iteration, add the number of keys of the current object to the accumulator to sum up the keys of every item:

  const users = [
  {
    firstName: "Bruce",
    lastName: "Wayne",
    id: "1",
  },

  {
    firstName: "Peter",
    lastName: "Parker",
    id: "2"
  },

  {
    firstName: "Tony",
    lastName: "Stark",
    id: "3"
  }
];

const totalProps = users.reduce((a, obj) => a + Object.keys(obj).length, 0);
console.log(totalProps);

edited Dec 15, 2018 at 6:25

Null isTrue

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answered Dec 15, 2018 at 5:23

CertainPerformance

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1 Comment

Null isTrue Over a year ago

Thank you very much, I was lost on how to go about this.

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