How to use a custom function in an ARRAYFORMULA for a range of cells?

Question

I have a Google Form that is populating a Google Sheet. Due to having custom formulas in the sheet to manipulate the data populated from the form I am using ARRAYFORMULA to apply to all rows in a column.

I have a custom function to encode rows containing html

function base64EncodeWebSafe(input) {

  try {
    // Try and fetch the specified url.
    return Utilities.base64EncodeWebSafe(input);

  } catch (e) { 
    Utilities.sleep(1000);
    return Utilities.base64EncodeWebSafe(input);

  }
}

When I call this function inside of ARRAYFORMULA(base64EncodeWebSafe(T2:T))

I receive an error "Cannot convert Array to (class)[]."

What I expect to happen is to apply the encoding function to the range T2:T

Answer 1

This is described in the Custom Functions guide . I've adapted the implementation used in the guide, but you could do something else. Basically, if using ARRAYFORMULA, then you need to treat the input as a 2-dimensional array.

function base64EncodeWebSafe(input) {
  if (input.map) { // Test whether input is an array.
    return input.map(base64EncodeWebSafe)
  } else {
    try {
      return Utilities.base64EncodeWebSafe(input);
    } catch (e) {
      Utilities.sleep(1000);
      return Utilities.base64EncodeWebSafe(input);
    }
  }
}