tribonacci sequence in javascript

1function tribonacci(signature,n){  
2  for (var i = 0; i < n-3; i++) { // iterate n times
3    signature.push(signature[i] + signature[i+1] + signature[i+2]); // add last 3 array items and push to trib
4  }
5  return signature.slice(0, n); //return trib - length of n
6}