# Javascript: 3 Ways to Calculate the Sum of an Array

This practical, succinct article walks you through three examples that use three different approaches to find the sum of all elements of a given array in Javascript (suppose this array only contains numbers). Without any further ado, let’s get started.

## Using Array.reduce() method

If you’re using modern Javascript (ES6 and beyond), this might be the neatest and quickest solution.

Example:

``````// define a reusable function
const calculateSum = (arr) => {
return arr.reduce((total, current) => {
}, 0);
}

// try it
console.log(calculateSum([1, 2, 3, 4, 5]));``````

Output:

``15``

The reduce() method executes a reducer function for elements of an array. It returns the accumulated result from the last call of the callback function. Below is the syntax:

``array.reduce(function(total, current, index, arr), initialValue)``

Where:

• total (required): The initial value, or the previously returned value of the function
• current (required): The current element
• current (optional): The index of the current element
• arr (optional): The array that the current element belongs to

## Using a classic For loop

This is an easy-to-understand approach and has been used for decades. However, the code is a bit longer.

Example:

``````// define a reusable function
function calculateSum(arr) {
var sum = 0;
for (var i = 0; i < arr.length; i++) {
sum += arr[i];
}
return sum;
}

// try it
console.log(calculateSum([1, 2, 3, 4]));``````

Output:

``10``

## Using modern For/Of loop

This approach also uses a loop but is more concise than the previous one. Like the Array.reduce() method, for/of was added to ES6 (JS 2015).

Example:

``````const arr = [9, 8, 7, 6, 5];
let sum = 0;
for (let e of arr){
sum += e;
}
console.log(sum);``````

Output:

``35``

## Conclusion

You’ve learned more than one technique to totalize all elements of a numeric array in Javascript. Keep the ball rolling and continue exploring more new and awesome stuff in the modern Javascript world by taking a look at the following articles:

You can also check out our Javascript category page, TypeScript category page, Node.js category page, and React category page for the latest tutorials and examples.

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