phpjs/functions/math/atan2.js

php.js offers community built php functions in javascript

function atan2(y, x) {
  //  discuss at: http://phpjs.org/functions/atan2/
  // original by: Brett Zamir (http://brett-zamir.me)
  //   example 1: atan2(1, 1);
  //   returns 1: 0.7853981633974483

  return Math.atan2(y, x);
}