Converting a column index to its corresponding column letter is a common need in Google Sheets. This can be achieved with Google Apps Script, a powerful automation tool for Google Workspace applications. Let's explore the code and understand how it works with a practical example:

Google Apps Script Code:

  // A function to convert a column index to the corresponding column letter
  function convertColumnIndexToLetter(index) {
    // Check for invalid indices
    if (index < 1 || index > 18278) {
      return "Invalid index";
    }
    
    var columnLetter = "";
    
    // Convert the index into a column letter
    while (index > 0) {
      var remainder = (index - 1) % 26;
      columnLetter = String.fromCharCode(65 + remainder) + columnLetter;
      index = Math.floor((index - 1) / 26);
    }
    
    return columnLetter;
  }
                  

Example:

Let's say you want to convert column index 28 to its corresponding column letter, which should be "AB." You can achieve this by calling the convertColumnIndexToLetter(28) function:

  // Convert index 28 to its corresponding column letter
  var columnLetter = convertColumnIndexToLetter(28);
  
  // The variable columnLetter will now contain "AB"
                

The code defines a function named convertColumnIndexToLetter that takes a column index as input and returns the corresponding column letter. It works by converting the index into a base-26 number, where each digit represents a letter in the alphabet. For example, column index 1 corresponds to "A," 27 corresponds to "AA," and so on.