Nodejs Fibonacci Sequence Get memoFib(hash=})

Method Source Code

/**//from   w  w w  .j  a v a 2s  .c om
 * Returns the Nth fibonacci number.
 * @extends Number
 * @function memoFib
 * @return {number}
 *
 * Examples:
 *     Number(20).memoFib();
 *     => 6765
 */
Number.prototype.memoFib = function (hash={}) {
  if (Number(this) < 0) return -1;
  else if (Number(this) === 0) return 0;
  else if (Number(this) === 1) return 1;
  else {
    prevFib = hash[this-1] || (hash[this-1] = (this-1).memoFib(hash));
    prevPrevFib = hash[this-2] || (hash[this-2] = (this-2).memoFib(hash));
    return prevFib + prevPrevFib;
  }
}

Related

1. iterFib()

   Number.prototype.iterFib = function () {
     var v1 = 0, v2 = 1, temp = 0;
     (new Array()).rangeArray(0, this-1).forEach(function(index) {
       temp = v2;
       v2 = v2 + v1;
       v1 = temp;
     });
     return v2;
   

2. naiveFib()

   Number.prototype.naiveFib = function () {
     if (Number(this) < 0)
       return -1;
     switch (Number(this)) {
       case 0:
         return 0;
       case 1:
         return 1;
       default:
   ...
   

3. sumFibs(num)

   Array.prototype.last = function() {
     return this[this.length-1];
   };
   Array.prototype.secondToLast = function() {
     return this[this.length-2];
   };
   function sumFibs(num) {
     var sequence = [1,1];
     while (sequence.secondToLast() + sequence.last() <= num) {
   ...