phpjs/functions/math/round.js

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function round(value, precision, mode) {
  //  discuss at: http://phpjs.org/functions/round/
  // original by: Philip Peterson
  //  revised by: Onno Marsman
  //  revised by: T.Wild
  //  revised by: Rafał Kukawski (http://blog.kukawski.pl/)
  //    input by: Greenseed
  //    input by: meo
  //    input by: William
  //    input by: Josep Sanz (http://www.ws3.es/)
  // bugfixed by: Brett Zamir (http://brett-zamir.me)
  //        note: Great work. Ideas for improvement:
  //        note: - code more compliant with developer guidelines
  //        note: - for implementing PHP constant arguments look at
  //        note: the pathinfo() function, it offers the greatest
  //        note: flexibility & compatibility possible
  //   example 1: round(1241757, -3);
  //   returns 1: 1242000
  //   example 2: round(3.6);
  //   returns 2: 4
  //   example 3: round(2.835, 2);
  //   returns 3: 2.84
  //   example 4: round(1.1749999999999, 2);
  //   returns 4: 1.17
  //   example 5: round(58551.799999999996, 2);
  //   returns 5: 58551.8

  var m, f, isHalf, sgn; // helper variables
  precision |= 0; // making sure precision is integer
  m = Math.pow(10, precision);
  value *= m;
  sgn = (value > 0) | -(value < 0); // sign of the number
  isHalf = value % 1 === 0.5 * sgn;
  f = Math.floor(value);

  if (isHalf) {
    switch (mode) {
      case 'PHP_ROUND_HALF_DOWN':
        value = f + (sgn < 0); // rounds .5 toward zero
        break;
      case 'PHP_ROUND_HALF_EVEN':
        value = f + (f % 2 * sgn); // rouds .5 towards the next even integer
        break;
      case 'PHP_ROUND_HALF_ODD':
        value = f + !(f % 2); // rounds .5 towards the next odd integer
        break;
      default:
        value = f + (sgn > 0); // rounds .5 away from zero
    }
  }

  return (isHalf ? value : Math.round(value)) / m;
}