Used with the hook.io microservice framework to calculate the date of Easter for a given year.

hooked.js

module['exports'] = function easter(hook) {
 
  var year = hook.params.year;
  hook.debug("i am going to calculate the date of Easter for " + year);
  
  // using the "Meeus/Jones/Butcher" algorithm
  var a = year % 19;
  var b = Math.floor(year/100);
  var c = year % 100;
  var d = Math.floor(b/4);
  var e = b % 4;
  var f = Math.floor((b + 8) / 25);
  var g = Math.floor((b - f + 1) / 3);
  var h = ((19*a) + b - d - g + 15) % 30;
  var i = Math.floor (c/4);
  var k = c % 4;
  var L = (32 + (2*e) + (2*i) - h - k) % 7;
  var m = Math.floor((a + (11*h) + (22*L)) / 451);
  var month = Math.floor((h + L - (7*m) + 114) / 31);
  var day = ((h + L - (7*m) + 114) % 31) + 1;
  
  hook.debug("month is " + month);
  hook.debug("day is " + day);
  var monthNames = [ "January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December" ];
    
  hook.res.end("Easter is " + monthNames[month-1] + " " + day + " in " + year + "\n");
 
};
 
module['exports'].schema = {
  "year": {
    "type": "number"
  }
};