# Function that merges arrays into one in JavaScript

Let's now implement the `merge` function, which takes an arbitrary number of arrays as parameters and merges their elements into one array.

Here is an example of how our function works:

`let result = merge([1, 2, 3], [4, 5, 6], [7, 8, 9]); console.log(result); // shows [1, 2, 3, 4, 5, 6, 7, 8, 9]`

Let's get down to implementation. Let's first get the passed arrays as a single two-dimensional one:

`merge([1, 2, 3], [4, 5, 6], [7, 8, 9]); function merge(...arrs){ console.log(arrs); // shows [ [1, 2, 3,] [4, 5, 6], [7, 8, 9] ] }`

Let's now merge this two-dimensional array into a one-dimensional one. We use the `concat` method and the spread operator for this:

`let arrs = [ [1, 2, 3,], [4, 5, 6], [7, 8, 9] ]; let result = [].concat(...arrs); console.log(result); // shows [1, 2, 3, 4, 5, 6, 7, 8, 9]`

Let's add this code to our `merge` function:

`function merge(...arrs) { return [].concat(...arrs); } let result = merge([1, 2, 3], [4, 5, 6], [7, 8, 9]); console.log(result); // shows [1, 2, 3, 4, 5, 6, 7, 8, 9]`

As you can see, this function also turned out to be very concise.

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