findMeanArray()

Step 1: Understand the problem and initialize the function

Before diving into the code, first understand what the problem is asking. In this case, the function should take an array of numbers as input and return the average or mean of those numbers. To start, initialize a function called findMeanArray which accepts an array arr as a parameter.

function findMeanArray(arr) {
    // Code will go here
}

Step 2: Handle an edge case

Consider an edge case where the input array is empty. In this case, the function should return 0 as there are no numbers to calculate the mean. Add the following conditional statement to the function:

function findMeanArray(arr) {
    if (arr.length === 0) {
        return 0;
    }
}

Step 3: Calculate the sum of numbers

To find the mean, we need to first calculate the sum of all numbers in the array. We can do that through JavaScript's reduce method which iterates over each element of the array and combines them into a single output value. Here, initialize a variable sum equal to the sum gotten from reducing the array.

function findMeanArray(arr) {
    if (arr.length === 0) {
        return 0;
    }
    
    var sum = arr.reduce(function(a, b) {
        return a + b;
    });
}

Step 4: Calculate the mean

After calculating the sum, to find the mean, we will divide the sum by the length of the array. Then return this mean value from our function.

function findMeanArray(arr) {
    if (arr.length === 0) {
        return 0;
    }
    
    var sum = arr.reduce(function(a, b) {
        return a + b;
    });
    
    return sum / arr.length;
}

Step 5: Test the function

Now let's test our function with an example input to make sure it's working as expected.

console.log(findMeanArray([2, 4, 6, 8, 10])); // output should be 6

If the function works correctly, it should output the average of the input numbers.

Conclusion

By following these steps, you can create a JavaScript function that calculates the mean of an array of numbers. This function is flexible and handles the edge case of empty inputs to avoid runtime errors. It uses JavaScript's built-in reduce method to calculate the sum, demonstrating a beneficial use of array methods in solving complex problems.