fibonacci.js

/*
Name:           fibonacci
Description:    This function calculates fibonacci numbers for endless iterations
Author:         Franklin (https://fvdm.com)
Source & docs:  https://github.com/fvdm/nodejs-fibonacci
Contact:        https://github.com/fvdm/nodejs-fibonacci/issues
License:        Unlicense (Public Domain, see LICENSE file)
*/

const bignum = require( 'bn.js' );
const { EventEmitter } = require( 'events' );

module.exports = new EventEmitter();
module.exports.doWhile = false;


/**
 * Start iteration
 *
 * @param   {number}  [limit=0]  Run fibonacci iterations
 * @return  {object}             result
 */

module.exports.iterate = function ( limit = 0 ) {
  let next = new bignum( 1 );
  let cur = new bignum( -1 );
  let last = new bignum( 0 );
  let loop = new bignum( 0 );
  let start = new Date().getTime();
  let result = {};

  limit = limit && new bignum( limit );
  module.exports.doWhile = true;

  while ( module.exports.doWhile ) {
    // prev cur -> now last
    // prev next -> now cur
    last = cur;
    cur = next;
    next = cur.add( last );

    result.number = next.toString();
    result.length = next.toString().length;
    result.iterations = loop.toString();
    result.ms = new Date().getTime() - start;

    module.exports.emit( 'result', result );

    // found the one
    if ( limit && loop.eq( limit ) ) {
      module.exports.doWhile = false;
      module.exports.emit( 'done', result );
    }

    // count
    loop = loop.add( new bignum( 1 ) );
  }

  return result;
};


/**
 * Stop iteration
 *
 * @return {void}
 */

module.exports.kill = function () {
  module.exports.doWhile = false;
};