array.prototype.unique.js

var states = ["Alabama", "Alaska", "Arizona", "Arkansas", "California", "Colorado", "Connecticut", "Delaware", "Florida", "Georgia", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", "Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico", "New York", "North Dakota", "North Carolina", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming", "Alabama", "Alaska", "Arizona", "Arkansas", "California", "Colorado", "Connecticut", "Delaware", "Florida", "Georgia", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", "Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico", "New York", "North Dakota", "North Carolina", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming"], 
    mega = [], 
    howmany = 100;


while(howmany--) {
  mega = mega.concat(states);
}



//  Generally, I see implementations that look like this...
Array.prototype.uniquedual = function() {
  
  var o = {}, i, l = this.length, r = [];
  
  
  for(i=0; i<l;i++) o[this[i]] = this[i];
  
  for(i in o) r.push(o[i]);
  
  return r;
};



console.log( mega.uniquedual() );


// Which got me thinking. And that resulted in this...
// It combines the tasks of the two loops into one
Array.prototype.unique = function() {
  var o = {}, r = [], i = 0, l = this.length;
  
  while (l--) {
    i++;
    !o[this[i]] && ( r[r.length] = this[i] );
    
    o[this[i]] = this[i];
  }
  
  return r;
};

console.log( mega.unique() );