Sum of object properties in an array

Question

I have an array with properties, take the following, for example:

var arrayPeople = [ { name: 'joe', job: 'programmer', age: 25, }, { name: 'bob', job: 'plumber', age: 30, }; ]; 

I want to create a function that will return their average age, this is what I have currently not working

 var ageAverage = function(array) { var age = 0, average; for (var i = 0; i < array.length; i++) { age += array[i].age; } average = age / array.length; return average; }; 

What I get when I run this function, Not a number

But I can work:

 var ageAverage = function(array) { var age = 0, average; for (var i = 0; i < array.length; i++) { age = array[0].age; } average = age / array.length; return average; }; 

The subtle difference is that I took + = and just made it =, and I removed the use of our variable and I just gave it the first index of the array. Therefore, at the same time, I know that the function correctly replaces the array of arrayPeople parameters, but there is something wrong in my for loop that I stop from 0 and 1 (arrayPeople indices).

PS I'm trying to do this on my own, and I'm not looking for someone to just make this problem for me, I would really appreciate some hints on what to fix or maybe I need to explore how to solve this problem .

Thanks!!

Answer 1

You need to initialize the variable age ( var age = 0 )

 var arrayPeople = [{ name: 'joe', job: 'programmer', age: 25, }, { name: 'bob', job: 'plumber', age: 30, }]; var ageAverage = function(array) { var age = 0, average; for (var i = 0; i < array.length; i++) { age += array[i].age; } average = age / array.length; return average; }; console.log( ageAverage(arrayPeople) ); 

in your version, age variable is undefined , and undefined += number (for example, 25) returns NaN ;

also change to ; in this line

from

 for (var i = 0, i < array.length; i++) { 

to

 for (var i = 0; i < array.length; i++) { 

Answer 2

Consider using map and reduce :

 arrayPeople. map(function(item){ return item.age; }). reduce(function(a, b){ return a + b; }, 0) / arrayPeople.length; 

Or just reduce as @KooiInc pointed out:

 arrayPeople.reduce(function (a,b) { return a + b.age; }, 0) / arrayPeople.length; 

---

Working example:

 var arrayPeople = [{ name: 'joe', job: 'programmer', age: 25, }, { name: 'bob', job: 'plumber', age: 30, }], average = arrayPeople.reduce(function(a, b) { return a + b.age; }, 0) / arrayPeople.length; document.write(average); 

Answer 3

You must change the value for:

for (var i = 0; i <array.length; i ++) instead of for (var i = 0, i <array.length; i ++)

and give the initial value of age

 var age=0 

Answer 4

There is always one line.

 arrayPeople.reduce((a, o, i, p) => a + o.age / p.length, 0)); 

 console.log(`${[{ name: 'joe', job: 'programmer', age: 25, }, { name: 'bob', job: 'plumber', age: 30, } ].reduce((a, o, i, p) => a + o.age / p.length, 0)}%`);