I am attempting to write a function that takes two arrays as inputs, representing the top and bottom halves of a deck of cards, and shuffles them together using recursion. I am attempting return a single array containing the elements from both input arrays interleaved, like so:

- the first element should be the first element of the first input array
- the second element should be the first element of the second input array,
- the third element should be the second element of the first input array,
- the fourth element should be the second element of the second array,

...etc.

I want to append any remaining elements to the end of the array.

This is how I solved it without recursion:

```
function shuffleCards(topHalf, bottomHalf) {
let returnArray = [];
for (let i = 0; i < Math.max(topHalf.length, bottomHalf.length); i++) {
if (topHalf[i]) {
returnArray.push(topHalf[i]);
}
if (bottomHalf[i]) {
returnArray.push(bottomHalf[i]);
}
}
return returnArray
}
```

and this is my attempt with recursion:

```
function shuffleCards(topHalf, bottomHalf) {
let results = [];
if (topHalf.length) {
results.push(topHalf[0]
}
if (bottomHalf.length) {
results.push(bottomHalf[0])
}
return results.concat(shuffleCards(topHalf.slice(1), bottomHalf.slice(1)));
}
```

I keep getting the syntax error "missing ) after argument list" but I am fairly certain all of the parenthesis are in the write place.

Any tips?

Thanks!

·

Juan Pablo Isaza

Beside missing parenthesis, you could take only the first item from the first half and call the function with swapped arrays.

```
function shuffleCards([value, ...topHalf], bottomHalf) {
return value === undefined
? [...bottomHalf]
: [value, ...shuffleCards(bottomHalf, topHalf)];
}
console.log(...shuffleCards([1, 2, 3, 4], [5, 6, 7, 8]));
```

·
Juan Pablo Isaza
Report

```
function shuffleCards(topHalf, bottomHalf,results = []) {
if(topHalf.length===0&&bottomHalf.length===0)return results;
if (topHalf.length!==0) {
results.push(topHalf[0])
}
if (bottomHalf.length!==0) {
results.push(bottomHalf[0])
}
return shuffleCards(topHalf.slice(1), bottomHalf.slice(1),results);
}
```

·
Juan Pablo Isaza
Report

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