## Objective

Create a function to multiply all the numbers in a given array and return the product.

## Description

Consider the following array of numbers:

`var nums = [1, 5, 70, -2, -1, -0.5];`

If we multiply all the numbers together, we get the value `-350`

.

In this exercise, you ought to create a function ** multiplyAll()** that takes in an array of numbers and returns back their product.

If the array is empty, the value returned should be `null`

.

Here are some examples of the usage of the function:

`multiplyAll([1, 5, 70, -2, -1, -0.5]);`

`multiplyAll([2, 2, 2]);`

`multiplyAll([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);`

`multiplyAll([]);`

## New file

Inside the directory you created for this course on JavaScript, create a new folder called **Exercise-24-Multiply-All** and put the .html solution files for this exercise within it.

## Solution

To start with, we'll deal with the special case, i.e. when the given array is empty, where we have to return `null`

:

```
function multiplyAll(arr) {
if (arr.length === 0) {
return null;
}
}
```

Proceeding forward, we lay out a variable ** product** to hold the product of itself and the current number during each iteration of the loop.

In the end, this variable effectively holds the product of *all* the numbers in the array.

Altogether, we get to the following code:

```
function multiplyAll(arr) {
if (arr.length === 0) {
return null;
}
var product = 1;
for (var i = 0; i < arr.length; i++) {
product *= arr[i];
}
return product;
}
```