Largest 5 digit number in a series

function solution(digits){
  let answer = 0;
  
  for (let i=0; i<digits.length; i++){
    let number = digits.substr(i, 5);  //each loop iteration pulls the next 5 digits into a substring
    if(Number(number) > answer){       //convert to number and compare against answer
      answer = Number(number);
    }
  }
  return answer;
}