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

Last Updated : 03 Jun, 2024

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:

Table of Content

Using foreach() loop
Using for loop with ParseInt() method
Using reduce() function
Using for...of Loop

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:

JavaScript

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));

Output

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:

JavaScript

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);

Output

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:

JavaScript

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);

Output

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:

JavaScript

// 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));