JavaScript Algorithms

binary-search-recursive.js

// Recursive Binary Search 
// Array must be sorted in ascending order
Array.prototype.binarySearch = function(num, from, to) {
  to = to || this.length-1;
  from = from || 0;

  if(!num || from > to) return null;

  var index = Math.floor((to-from) / 2) + from;
  if(num < this[index]) return this.binarySearch(num, from, index-1);
  if(num > this[index]) return this.binarySearch(num, index+1, to);
  return index;
};

// How to use:
[1,2,3,4,5].binarySearch(5); // 4

event-emitter.js

function EventEmitter() {
  this.events = {};
}
EventEmitter.prototype.addEventListener = function(ev, cb, ctx) {
  this.events[ev] = this.events[ev] || [];
  this.events[ev].push(cb.bind(ctx));
};
EventEmitter.prototype.emit = function(ev, args) {
  (this.events[ev] || []).forEach(function(cb) {
    cb(args);
  });
};

state-machine.js

function StateMachine(state, sMin, sMax) {
  this.state = state || 0;
  this.sMin = sMin || 0;
  this.sMax = sMax || 1;

  this.minChangeTime = 1250;
  this.lastChanged = 0;

  EventEmitter.call(this);
}
StateMachine.prototype = Object.create(EventEmitter.prototype);
StateMachine.prototype.changeState = function(nState) {
  var t = new Date();
  if (nState >= this.sMin && nState <= this.sMax && t - this.lastChanged > this.minChangeTime) {
    this.emit("stateChange", {
      oldState: this.state,
      newState: nState
    });
    this.state = nState;
    this.lastChanged = t;

    if (nState === 0 || nState === 2) {
      this.minChangeTime = 1250;
    } else {
      this.minChangeTime = 1000;
    }
  }
};