Javascript Array distinct()

Array.prototype.distinct = function () {
    var known = {};
    var result = [];

    this.forEach(item =>  {/* ww w .  j  av  a 2s .  co m*/
            if (!known[item]) {
                known[item] = true;
                result.push(item);
            }
        });

    return result;
};

/**/*from  w w  w  .  java2 s  .c o m*/
 * author: oldj
 * blog: http://oldj.net
 */

Array.prototype.distinct = function () {

  var d = {},
    i;

  this.push(d);
  while ((i = this.shift()) != d) {
    if (!d.hasOwnProperty(i)) {
      this.push(i);
      d[i] = 1;
    }
  }

  return this;
};

Array.prototype.distinct = function() {
    var ret = [];
    for (var i = 0; i < this.length; i++) {
        for (var j = i + 1; j < this.length; ) {
            if (this[i] === this[j]) {
                ret.push(this.splice(j, 1)[0]);
            } else {/*ww w  . ja va  2  s  .  c  o  m*/
                j++;
            }
        }
    }
    return ret;
};
console.log([1, 2, 3, 4, 4, "4", 5].distinct());

//  Way 1;//from ww w . j av  a2  s .co m
Array.prototype.distinct = function(){
 for(var i = 0; i< this.length; i++){
  var n = this[i];
  this.splice(i, 1);
  if(this.indexOf(n) < 0){
   this.splice(i,1,n);
  }
 }
 return this;
}

Array.prototype.distinct2 =  function(){
 var _self = this;
 var _a = this.concat().sort();
 console.log(_a);

 _a.sort(function(a,b){
  console.log("a: "+ a, "b: "+ b);
  if(a == b){
   var n = _self.indexOf(a);
   _self.splice(n, 1);
  }
 });
 return _self;
}

Array.prototype.distinct = function() {
  var ret = [];//from  w  w w. j  a  va2s  .c o  m
  for (var i = 0; i < this.length; i++){
    for (var j = i+1; j < this.length;) {
      if (this[i] === this[j]) {
        ret.push(this.splice(j, 1)[0]);
      } else {
        j++;
      }
    }
   }
  return ret;
};

//for test
var a = ['a','b','c','d','b','a','e','d','b','a','e'];
var b = a.distinct();
console.log(a);
console.log(b);

Array.prototype.distinct = function () {
 var n = {}, r = [];
 for (var i = 0; i < this.length; i++) {
  if (!n[this[i]]) {
   n[this[i]] = true;/*from   www  . j a  v  a  2s  .c o m*/
   r.push(this[i]);
  }
 }
 return r;
}

Array.prototype.distinct = function () {
    return this.filter(function (element, position, self) {
        return self.indexOf(element) == position;
    });/*from  w  w  w .j  a v  a  2 s . c om*/
};