Step 1: Understanding the problem

We are tasked with creating a function, findArrayAverage, that takes an array of numbers as an input and returns the average of those numbers. In other words, this function must sum up all the numbers in the array, and then divide this sum by the number of elements in the array.

Step 2: Defining the function

Let's start by defining a simple function, findArrayAverage, which takes one parameter, numbers. For now, this function won't do anything - it's an empty shell.

function findArrayAverage(numbers) {

}

Step 3: Calculating the sum of the array elements

The first part of our task is to calculate the sum of all the numbers in the array. We can accomplish this using the reduce function in JavaScript.

The reduce function applies a function to each item of the array, in order, so as to reduce the array to a single output value. In our case, this function should take two inputs (the current sum and the current number) and return their sum.

function findArrayAverage(numbers) {
    let sum = numbers.reduce(function(a, b) {
        return a + b;
    }, 0);
}

Step 4: Calculating and returning the average

Having obtained the sum of the array elements, the remaining task is simple. The average of a list of numbers is equal to the sum of those numbers, divided by the number of those numbers. We can get the number of items in our array using the length property, and return the final computed average from the function.

function findArrayAverage(numbers) {
    let sum = numbers.reduce(function(a, b) {
        return a + b;
    }, 0);

    return sum / numbers.length;
}

Conclusion

Now our findArrayAverage function is complete. This function can be used to find the average of any array of numbers.

Here's the complete function:

function findArrayAverage(numbers) {
    let sum = numbers.reduce(function(a, b) {
        return a + b;
    }, 0);

    return sum / numbers.length;
}

For example, calling findArrayAverage([1, 2, 3, 4, 5]) would return 3 (since that's the average of the numbers 1, 2, 3, 4, and 5).

With this function, calculating an array average is now an easy task!