Convert Spreadsheet Column Index to Letter

In Google Sheets, the columns are indexed with numbers, starting from 1. However, for convenience, they are also commonly referred to using letters (e.g., "A" for the first column, "D" for the fourth column). This conversion between numerical indices and letter values is often necessary for scripting tasks.

One way to achieve this conversion is through the following function:

function getColumnLetterByIndex(index) {
  var letter = String.fromCharCode(64   index);
  return letter;
}

Using this function:

• getColumnLetterByIndex(4); returns "D"
• getColumnLetterByIndex(1); returns "A"
• getColumnLetterByIndex(6); returns "F"

As seen in the examples, the index parameter corresponds to the numerical column index in the spreadsheet.

Note that this function does not handle column numbers greater than 26, which would require using a double-letter representation (e.g., "AA" for column 27). For more complex scenarios, custom functions or external libraries may be necessary.