Find average of each array within an array in JavaScript

We are required to write a JavaScript function that takes in an array of arrays of Numbers. The function should create a new array, compute the average for each subarray and push it at the corresponding indices in the new array.

Let’s say the following is our array −

const arr = [
   [1],
   [2,3],
   [4,5,6,7]
];

Example

The code for this will be −

const arr = [
   [1],
   [2,3],
   [4,5,6,7]
];
const average = (arr = []) => {
   const sum = arr.reduce((a, b) => a + b);
   return sum / arr.length;
}
const averageWithin = (arr = []) => {
   const res = arr.map(el => average(el));
   return res;
};
console.log(averageWithin(arr));

Output

And the output in the console will be −

[ 1, 2.5, 5.5 ]