Text at a data boundary needs both parsing and validation. JSON.parse checks JSON syntax, but the parsed value can still have the wrong shape. Validate the array and its elements before treating it as a string list. Regular expressions solve a different problem: checking or extracting text that follows a defined pattern. Anchors require the whole string to match, and a capture group isolates the part you need to convert. JSON.stringify can also use an allowed-key list to limit public output. The exercises combine these ideas around fictional route codes and public records. Keep malformed input separate from a valid zero or an empty string.