How to Find the Sum of an Array of Numbers in JavaScript?

There are multiple approaches to finding the sum of an array of numbers in JavaScript.

1. Using for Loop

The for loop is a basic and widely used approach to sum the elements of an array. Initialize a variable to store the sum and iterate through the array, adding each element to the sum.

let arr = [10, 20, 30, 40, 50];
let sum = 0;

for (let i = 0; i < arr.length; i++) {
    sum += arr[i];
}

console.log(sum); // Output: 150

2. Using for…of Loop

The for...of loop, introduced in ES6, simplifies iterating over array elements without needing to manage indices.

let arr = [10, 20, 30, 40, 50];
let sum = 0;

for (let num of arr) {
    sum += num;
}

console.log(sum); // Output: 150

3. Using reduce() Method

The reduce() method is a powerful functional programming approach to accumulate values in an array, making it ideal for calculating sums.

let arr = [10, 20, 30, 40, 50];
let sum = arr.reduce((accumulator, currentValue) => accumulator + currentValue, 0);

console.log(sum); // Output: 150

4. Using forEach() Method

The forEach() method iterates over each element of the array and allows you to update an external variable.

let arr = [10, 20, 30, 40, 50];
let sum = 0;

arr.forEach(num => {
    sum += num;
});

console.log(sum); // Output: 150

5. Using eval() Method (Not Recommended)

You can convert the array to a string and use eval() method to compute the sum. However, this method is not recommended due to security and readability issues.

let arr = [10, 20, 30, 40, 50];
let sum = eval(arr.join('+'));

console.log(sum); // Output: 150

7. Using Recursion

You can calculate the sum of an array recursively, although it’s less efficient for large arrays.

function sumArray(arr) {
    if (arr.length === 0) 
        return 0; // Base case
    return arr[0] + sumArray(arr.slice(1)); // Recursive case
}

let arr = [10, 20, 30, 40, 50];
console.log(sumArray(arr)); // Output: 150

8. Using Lodash _.sum() Method

If you’re already using Lodash in your project, the _.sum() method provides a simple way to sum array elements.

const _ = require('lodash');

let arr = [10, 20, 30, 40, 50];
let sum = _.sum(arr);

console.log(sum); // Output: 15