Mean of an array rounded down to nearest integer in JavaScript

Problem

We need to write a JavaScript function that takes an array of numbers and returns the average (mean) of the array rounded down to the nearest integer using Math.floor().

Example

Following is the code ?

const arr = [45, 23, 67, 68, 12, 56, 99];

const roundedMean = (arr = []) => {
    const { sum, count } = arr.reduce((acc, val) => {
        let { sum, count } = acc;
        count++;
        sum += val;
        return { sum, count };
    }, {
        sum: 0, count: 0
    });
    
    const mean = sum / (count || 1);
    return Math.floor(mean);  // Round down to nearest integer
};

console.log(roundedMean(arr));

Output

52

Alternative Approach Using Array Methods

Here's a more concise solution using built-in array methods:

const arr = [45, 23, 67, 68, 12, 56, 99];

const roundedMeanSimple = (arr = []) => {
    if (arr.length === 0) return 0;
    
    const sum = arr.reduce((total, num) => total + num, 0);
    const mean = sum / arr.length;
    return Math.floor(mean);
};

console.log(roundedMeanSimple(arr));

// Test with different arrays
console.log(roundedMeanSimple([10, 20, 30]));     // 20
console.log(roundedMeanSimple([15, 25, 35]));     // 25
console.log(roundedMeanSimple([]));               // 0

52
20
25
0

Key Points

• Math.floor() rounds down to the nearest integer, while Math.round() rounds to the nearest integer
• The function handles empty arrays by returning 0
• Using reduce() provides a functional programming approach to calculate the sum
• For the array [45, 23, 67, 68, 12, 56, 99], the mean is 52.857..., which rounds down to 52

Conclusion

To find the mean of an array rounded down, calculate the sum using reduce(), divide by array length, and apply Math.floor(). This approach handles edge cases and provides accurate results for any numeric array.