Swizzle array function for Google Sheets

swizzle_array.js

////
// Return an array of cells that match a reference string in the input_cell
// Example:
//     W | 5
//     X | 3
//     Y | 6
//     Z | 5
//
// 
// SWIZZLE_ARRAY("WXX", A1:D2) will return [A2,B2,B2]
// Best used with SUM, e.g. =SUM(SWIZZLE_ARRAY(...))
//
// @param input_cell      A cell containing a string of letters to lookup
// @param reference_array A 2D array, where the first column contains letters and 
//                        the second column contains values
// @returns array or null
function SWIZZLE_ARRAY(input_cell, reference_array) {
  // Do some initial validation  
  if (input_cell.map) {
    throw("Input cell must be a single cell, not an array")
  }
  
  if (!reference_array.map) {
    throw ("Reference_array is not a valid selection [should be a 2 column array]");
  }
  
  var swizzle = "";
  var matching_cells = [];
  var characters = input_cell.split("");
  
  for (var i = 0; i < characters.length; i++) {
    let char = characters[i];
    
    for (var j = 0; j < reference_array.length; j++) {
      // Compare this character with the first column of this array)
      if (reference_array[j][0] == char) {
        // It matches! Add the "value" cell (second column) to our matching cell list
        matching_cells.push(reference_array[j][1])
      }
    }
  }
  
  if (matching_cells.length > 0) {
    return matching_cells;
  }
  return null
}