Using built-in spreadsheet functions in a script

Question

I\'m using Google App Script for the first time. I\'m using it on a Google Doc spreadsheet.

I\'m trying very simple functions, just to learn the basics. For example

Answer 1

What the spreadsheet functions can do, Javascript can do. I just have to replace var day_num = weekday() by var day_num = new Date(date).getDay()

Here is the result :

/**
* Writes the day of the week (Monday, Tuesday, etc), based on a date
*/
function day_name(date) {
  // calculate day number (between 1 and 7)
  var day_num = new Date(date).getDay();

  // return the corresponding day name
  switch(day_num) {
    case 0: return 'Sunday';    break;
    case 1: return 'Monday';    break;
    case 2: return 'Tuesday';   break;
    case 3: return 'Wednesday'; break;
    case 4: return 'Thursday';  break;
    case 5: return 'Friday';    break;
    case 6: return 'Saturday';  break;
  }
  return 'DEFECT - not a valid day number';
};