Google Form Response Notifications

// Change this variable value to match the name of the 'extra' sheet/tab holding the notification table.
var notification_sheet = "Notifications";

function get_Notification_Routing() {
  
  // Firstly, we need to get the sheet with the notification information in.
  // This uses 'method chaining', which means we can call one function after another.
  var sheet = SpreadsheetApp.getActive().getSheetByName(notification_sheet);
  
  // Once we have the sheet, we can find out what the last column and last row used (e.g. the extent of the data range).
  var last_col = sheet.getLastColumn(), last_row = sheet.getLastRow();
  
  // Using this, and with another method chain, we can get data from this range (this will include headers too)
  var routing_Data = sheet.getRange(1, 1, last_row, last_col).getValues();
  
  // This declares an 'object' that will hold our names/values and email addresses.
  var routing = {field : routing_Data[0][0], routes : {}};
  
  // This loops through all the data (starting at 1, because we are ignoring the headers)
  for (var i = 1; i < routing_Data.length; i++) {
    
    // The first column (0 as we start from zero) is the name/value
    var name = routing_Data[i][0];
    
    // The second column is the email address
    var email = routing_Data[i][1];
    
    // Here we set the email address
    routing.routes[name] = email;
    
  }
  
  // The return statement means we give this data back to the code from which this function was called.
  return routing;
}

// This is the catch-all address (e.g. if there isn't an email for a particular value). In this case, notifications will be sent here.
// If it is set to nothing (e.g. var default_email;) then notifications will only be sent when a match is found.
var default_email = "email@example.com";

function handle_onSubmit(e) {
  
  /* 
    This function is set up as a 'handler' for a specific event. It is done through 'Resources' -> 'Current Project's Triggers'.
    In practice, it means that this function will be run whenever that event occurs. In this case, we will use the 'On Form Submit' event.
    This should be fired every time a form response is submitted (either originally, or when it has been edited.
    The 'e' parameter holds all the information that has been submitted as part of the response.
    The code will run 'as' the user who created the trigger, so emails etc will come from them, not from the response submitting user.
  */
  
  // First we 'get' the route for the email we want to send.
  var routing = get_Notification_Routing();
  
  // We then can get the user, value and the email that we need to send to.
  var user_submitting_form = e.namedValues["Username"][0];
  var value_to_send_to = e.namedValues[routing.field][0];
  var email_to_send_to = routing.routes[value_to_send_to] ? routing.routes[value_to_send_to] : default_email;
  
  // Here we are 'building' the body content of the email by outputting each field name/value from the form.
  var email_Body = "";
  for (field in e.namedValues) {
    email_Body = email_Body + field + ": " + e.namedValues[field][0] + "\n";
  }
    
  // This checks to see if we have an email to send to!
  if (email_to_send_to) {
  
    // Send the email. The function call is formatted slightly differently (over multiple lines) to make it more 'readable'
    MailApp.sendEmail(
      email_to_send_to,
      user_submitting_form ? "New Form Request from: " + user_submitting_form : "New Form Request",
      email_Body
    );
  
  }
  
}