Javascript Array removeDuplicate()

// Remove Dupes from Google Reader v0.2
///*  w  w w . jav a2 s  .  c om*/
// version 0.2 - 2008-05-28
// - moved Remove Dupes button next to the Refresh button
// - dupes: mark as read, but no longer hides them (fix keyboard j,k bug)
// - finds more dupes by splitting symbols (-, |)
// - more helpful firebug console output (ie. # dupes removed)
//
// version 0.1 - 2008-02-09
// - first revision
//
// Last Updated 2008-05-28
// Copyright (c) 2008, Hao Chen
// Released under the GPL license
// http://www.gnu.org/copyleft/gpl.html
// --------------------------------------------------------------------
// Contact: detect [at] hotmail [dot] com
// --------------------------------------------------------------------
//
// ==UserScript==
// @name          Remove Dupes from Google Reader
// @description   Because duplicate posts suck.
// @include       http://www.google.com/reader/*
// ==/UserScript==

Array.prototype.removeDuplicate = function() {
  // Here we remove duplicate values from the array of entries
  var array4 = new Array;
  var len = this.length;
  var entries = document.getElementById('entries');
  for (var i = 0; i < len; i++) {
    iboth = this[i];
    indexDash = iboth.lastIndexOf(' - ');
    if (indexDash != -1) {
      ititle = iboth.substr(0, indexDash);
    } else {
      ititle = iboth;
    }
    indexSlash = ititle.indexOf(' | ');
    if (indexSlash != -1) {
      ititle2 = ititle.substr(indexSlash + 3, ititle.length);
    } else {
      ititle2 = ititle;
    }
    var xx = true;
    for (var j = i + 1; j < len; j++) {
      jboth = this[j];
      indexDash = jboth.lastIndexOf(' - ');
      if (indexDash != -1) {
        jtitle = jboth.substr(0, indexDash);
      } else {
        jtitle = jboth;
      }
      indexSlash = jtitle.indexOf(' | ');
      if (indexSlash != -1) {
        jtitle2 = jtitle.substr(indexSlash + 3, jtitle.length);
      } else {
        jtitle2 = jtitle;
      }
      if (iboth == jboth || ititle == jtitle || ititle2 == jtitle2) xx = false;
    }
    if (xx == true) {
      array4.push(iboth);
    } else {
      var entry = entries.childNodes[i];
      entry.className = entry.className.replace('unread', '') + " read";
      console.log("Dupe removed: " + ititle);
    }
  }
  console.log(len - array4.length, "dupes marked as read.");
  return array4;
}

Array.prototype.removeDuplicate = function() {
 return this.reduce(function(last,current){
  if(last.indexOf(current) === -1){
   last.push(current);//w w  w  .  j  a  va2s.  c o  m
  }
  return last;
 },[])
};



var array = [1,1,2,1,3,4,12,4,5,,12,3,4];
var a = array.concat([]);
a = a.filter(function(item, pos) {
    return a.indexOf(item) == pos;
})
console.log(a)

console.log(array.removeDuplicate());

Array.prototype.removeDuplicate = function() {
  var result = [];
  var dict = {};/*ww  w.ja  v a 2 s  .  co m*/
  for (var i = 0, len = this.length; i < len; ++i) {
    if (!dict[this[i]]) {
      result.push(this[i]);
      dict[this[i]] = 1;
    }
  }
  return result;
};

var arr = [1, 1, 2, 3, 3, 4, 5, 6, 3, 2];
console.log(arr.removeDuplicate());

Array.prototype.removeDuplicate = function() {
 var obj = {};//  w  ww  . j a va2 s  .  co m
 var arr = [];
 this.forEach(function(value, index) {
  if (!obj[value]) {
   arr.push(value);
   obj[value] = true;
  }
 })
 return arr;
}