How to compute the average of an array after mapping each element to a value in JavaScript ?

Given an array, the task is to compute the average of an array after mapping each element to a value.

Input : arr=[2, 3, 5, 6, 7]
Output: 4.6
Explanation : (2+3+5+6+7)/5 = 4.6 

Input : [5,7,2,7,8,3,9,3]
Output: 5.5
Explanation : (5+7+2+7+8+3+9+3)/8 = 5.5 

Here are some common approaches:

Using foreach() loop

• Iterate the array elements using foreach() loop.
• Store the sum of each element in a variable.
• The average of all elements will be sum/length where length is the size of the given array.

Example:

let arr = [2, 3, 5, 6, 7];

// Function to calculate the average of numbers
function avg(arr) {
    let sum = 0;

    // Iterate the elements of the array
    arr.forEach(function (item, idx) {
        sum += item;
    });

    // Returning the average of the numbers
    return sum / arr.length;
}

console.log(avg(arr));

4.6

Using for loop with ParseInt() method

• Iterate the  numbers of the array using for loop
• Use  ParseInt() function to parse the numbers in decimal format.
• Store the sum of numbers in a variable.
• The average of all elements will be sum/length where length is the size of the given array.

Example:

arr = [2, 3, 5, 6, 7];
var sum = 0;

// Iterating the elements of the loop
for (var i = 0; i < arr.length; i++) {

    // Store the sum of all numbers
    sum += parseInt(arr[i], 10);
}

// Taking the average
var avg = sum / arr.length;

console.log(avg);

4.6

Output:

 4.6

Using reduce() function

• In this approach, We reduce i.e replace two numbers of the array with their sum in the original array.
• reduce() function returns a single value i.e the sum of all the numbers of the array.
• Store the return value in a variable (sum variable used).
• The average of all elements will be sum/length where length is the size of the given array.

Example:

var arr = [1, 2, 3, 4];
// Callback function calculating 
// the sum of two numbers
function check(a, b) {
    return a + b;
}

// Reducing the numbers of the array
var sum = arr.reduce(check);

// Calculating the average of the numbers
var avg = sum / arr.length;

console.log(avg);

2.5

Using for...of Loop

In this approach, we iterate over each element in the array using the for...of loop to calculate the sum of the elements, and then compute the average.

• We initialize a variable sum to 0 to keep track of the sum of the array elements.
• The for...of loop is used to iterate over each element in the array. For each iteration, we add the current element's value to the sum.
• After iterating through all elements, we calculate the average by dividing the sum by the length of the array.

Example:

// Define the array
let arr = [5, 7, 2, 7, 8, 3, 9, 3];

// Function to calculate the average using for...of loop
function avg(arr) {
    let sum = 0;
    
    // Iterate over the elements of the array
    for (let value of arr) {
        sum += value;
    }
    
    // Calculate the average
    return sum / arr.length;
}

// Call the function and log the output
console.log(avg(arr));

5.5