reduceRight.js

/*
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/ReduceRight
*/
// Production steps of ECMA-262, Edition 5, 15.4.4.22
// Reference: http://es5.github.io/#x15.4.4.22
if (!Array.prototype.reduceRight) {
  Array.prototype.reduceRight = function(callback, initialValue) {

    if (this === void 0 || this === null) {
      throw new TypeError('Array.prototype.reduceRight called on null or undefined');
    }

    if (callback.__class__ !== 'Function') {
      throw new TypeError(callback + ' is not a function');
    }

    var t = Object(this), len = t.length >>> 0, k = len - 1, value;
    if (arguments.length > 1) 
      {
        value = initialValue;
      } 
    else 
      {
        while (k >= 0 && !(k in t)) {
          k--;
        }
        if (k < 0) {
          throw new TypeError('Reduce of empty array with no initial value');
        }
        value = t[k--];
      }
      
    for (; k >= 0; k--) {
      if (k in t) {
        value = callback(value, t[k], k, t);
      }
    }
    return value;
  };
}