# Get the Sum of an Array of Numbers in JavaScript Thu Oct 14 20212 min read ## Get the Sum of an Array of Numbers#

To get the sum of an array of numbers:

1. Use the `reduce()` method to iterate over the array, passing it a function as the first parameter and an initial value of `0` as the second.
2. On each iteration increment the accumulated sum with the current value of the array.
index.js
```Copied!```const arr = [5, 15, 45];

const sum = arr.reduce((accumulator, value) => {
return accumulator + value;
}, 0);

console.log(sum); // 👉️ 65
``````

The `accumulator` parameter is initially set to `0`, because that's what we passed as the second parameter to the reduce method.

With each iteration, we increment the `accumulator` with the current value of the array until we calculate the total.

An alternative and perhaps simpler approach is to use a `for...of` loop.

To get the sum of an array of numbers:

1. Declare a `sum` variable using the `let` keyword and set it to `0`.
2. Use the `for...of` loop to iterate over the array and on each iteration increment the `sum` variable with the current value.
index.js
```Copied!```const arr = [5, 15, 45];

let sum = 0;

for (const value of arr) {
sum += value;
}

console.log(sum); // 👉️ 65
``````

The for...of loop allows us to iterate over an array.

Notice that we declare the `sum` variable using the `let` keyword. Had we declared the variable using `const`, we wouldn't be able to reassign it.

On each iteration we increment the value stored in the `sum` variable until we get the total.

The `for...of` loop is not supported by Internet Explorer. If you have to support the browser, use a basic for loop instead.
index.js
```Copied!```// Supported by IE

const arr = [5, 15, 45];

let sum = 0;

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

console.log(sum); // 👉️ 65
``````

In this example, we achieve the same result using a basic for loop instead of a `for...of` loop.

It is a bit harder to read and more cluttered, however if you have to support Internet Explorer, it gets the job done. 