# Get the Sum of an Array of Numbers in TypeScript Tue Mar 08 20222 min read Photo by Joel

## Get the Sum of an Array of Numbers in TypeScript#

To get the sum of an array of numbers:

1. Use the `reduce()` method to iterate over the array
2. On each iteration, increment the accumulated sum with the current value.
3. The result will be the sum of all the numbers in the array.
index.ts
```Copied!```const arr: number[] = [10, 20, 50];

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

console.log(result); // 👉️ 80
``````

The function we passed to the Array.reduce method gets invoked with each element (number) in the array.

The `accumulator` parameter gets an initial value of `0`, because that's what we supplied 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.

The `reduce()` method returns the sum of all of the numbers in the array.

You might also see examples that explicitly set the `accumulator` and return type of the `reduce()` method.

index.ts
```Copied!```const arr: number[] = [10, 20, 50];

// 👇️ using <number> generic to set return type
const result = arr.reduce<number>((accumulator, current) => {
return accumulator + current;
}, 0);

console.log(result); // 👉️ 80
``````

The example above uses a generic to explicitly set the type for the `accumulator` variable and the return type of the `reduce()` method.

However, in this situation it can be omitted, as TypeScript is able to infer it based on the provided default value.

An alternative and perhaps simpler approach is to use the `forEach` method.

To get the sum of an array of numbers:

1. Initialize a `sum` variable, using the `let` keyword and set it to `0`.
2. Call the `forEach()` method to iterate over the array.
3. On each iteration, increment the `sum` variable with the current number.
index.ts
```Copied!```const arr: number[] = [10, 20, 50];

let sum = 0;

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

console.log(sum); // 👉️ 80
``````

The function we pass to the Array.forEach method gets called with each element in the array.

Notice that we declare the `sum` variable using the `let` keyword. We can't reassign variables declared using `const`.

On each iteration of the loop, we increment the value stored in the `sum` variable to get the total amount.

This approach is more readable and intuitive, especially if you're not used to how the `reduce` method works.

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