.reduce()

Simply put ‘sum’ of an array, will work its way through an array, index by index, and add each value to a running total. At the end of the Array, the total is returned; Hooray! 🥳

In action:

const sumArray = array.reduce(
( previousValue, currentValue ) => previousValue + currentValue.age,
0);
console.log(sumArray); //Output 290

The important thing here is:

currentValue.age

It can do a lot more but ill investigate this in the future.

Array referenced above:

const array = [
  {
    id: 1,
    firstName: "John",
    lastName: "Doe",
    age: 50,
    eyeColor: "blue",
  },
  {
    id: 2,
    firstName: "Jane",
    lastName: "Doe",
    age: 40,
    eyeColor: "green",
  },
  {
    id: 3,
    firstName: "Dan",
    lastName: "Petersen",
    age: 200,
    eyeColor: "brown",
  },
];

Resources:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce