["A", "b", "C"] should return --> ["1: a", "2: b", "3: C"] but is instead returning --> ["1: a", "1: b", "1: C"]

/*
Write a function which takes a list of strings and returns each line prepended by the correct number.
The numbering starts at 1. The format is "num: string". Notice the colon and space in between.
Examples: (Input --> Output)

[] --> []
["a", "b", "c"] --> ["1: a", "2: b", "3: c"]
*/

function orderedArray(array) {
  if (array != []) {
    let num = 1;
    let prefix = `${num}: `;
    for (let i = 0; i < array.length; i++) {
      let prefix = `${i+1}: `;
      array[i] = prefix + array[i];
      num++;
    }
    return array;
  }
  return array;
}