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1309. Decrypt String from Alphabet to Integer Mapping

Given a string s formed by digits ('0' - '9') and '#' . We want to map s to English lowercase characters as follows:
Characters ('a' to 'i') are represented by ('1' to '9') respectively.
Characters ('j' to 'z') are represented by ('10#' to '26#') respectively.
Return the string formed after mapping.
It's guaranteed that a unique mapping will always exist.

• Example 1:
  Input: s = "10#11#12"
  Output: "jkab"
  Explanation: "j" -> "10#" , "k" -> "11#" , "a" -> "1" , "b" -> "2".

• Example 2:
  Input: s = "1326#"
  Output: "acz"

• Example 3:
  Input: s = "25#"
  Output: "y"

var freqAlphabets = function(s) {
  const map = { "1":"a", "2":"b", "3":"c", "4":"d", "5":"e",
				"6":"f", "7":"g", "8":"h", "9":"i", "10":"j", 
				"11":"k", "12":"l", "13":"m", "14":"n", "15":"o",
				"16":"p", "17":"q", "18":"r", "19":"s", "20":"t",
				"21":"u", "22":"v", "23":"w", "24":"x", "25":"y",
				"26":"z" };
  let result = '';
  for (let i = 0; i < s.length; ++i) {
    result += map[s[i + 2] === '#' ? (i += 2, s[i - 2] + s[i - 1]) : s[i]];
  }
  return result;
};