Array.prototype.distinct = function (){
  var arr = this,
    i,
    obj = {},
    result = [],
    len = arr.length;
  for(i = 0; i< arr.length; i++){
    if(!obj[arr[i]]){  //如果能查找到，證明數(shù)組元素重復(fù)了
      obj[arr[i]] = 1;
      result.push(arr[i]);
    }
  }
  return result;
};

Array.prototype.distinct = function(){
  var arr = this,
    result = [],
    i,
    j,
    len = arr.length;
  for(i = 0; i < len; i++){
    for(j = i + 1; j < len; j++){
      if(arr[i] === arr[j]){
        j = ++i;
      }
    }
    result.push(arr[i]);
  }
  return result;
}

Array.prototype.distinct = function (){
  var arr = this,
    len = arr.length;
  arr.sort(function(a,b){    //對數(shù)組進行排序才能方便比較
    return a - b;
  })
  function loop(index){
    if(index >= 1){
      if(arr[index] === arr[index-1]){
        arr.splice(index,1);
      }
      loop(index - 1);  //遞歸loop函數(shù)進行去重
    }
  }
  loop(len-1);
  return arr;
};

Array.prototype.distinct = function (){
  var arr = this,
    result = [],
    len = arr.length;
  arr.forEach(function(v, i ,arr){    //這里利用map，filter方法也可以實現(xiàn)
    var bool = arr.indexOf(v,i+1);    //從傳入?yún)?shù)的下一個索引值開始尋找是否存在重復(fù)
    if(bool === -1){
      result.push(v);
    }
  })
  return result;
};

function dedupe(array){
  return Array.from(new Set(array));
}
dedupe([1,1,2,3]) //[1,2,3]

let arr = [3,5,2,2,5,5];
let unique = [...new Set(arr)];  //[3,5,2]