Question

所以我尝试了所有我知道的东西。使用地图和过滤器，原型。没工作。

[{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}]

所以我想要实现的是，当我使用javascript执行ajax时，检查两个或更多对象是否具有相同的类型值，如果有两个或更多bmw-s，则删除其他对象并推送一个宝马类型的对象。希望我很清楚。提前致谢

Answer 1

function removeDuplicates(arr) {
  var alreadyExist = {};           // hash object to keep track of elemnt that have already been encountered
  var indexes = [];                // array of indexes that will be removed
  arr.forEach(function(o, i) {     // for each object o in arr
    if(alreadyExist[o.type])       // if the type of the object o at index i already exist
      indexes.push(i);             // mark its index i to be removed later
    else                           // if not
      alreadyExist[o.type] = true; // then mark the object as found so other ones will be removed
  });
  
  // for each index in the indexes array
  for(var i = 0; i < indexes.length; i++)
    arr.splice(indexes[i] - i, 1); // remove the object at that index ( - i because the array arr is continually changing. Its length decrease every time we remove an item)
}

var array = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"red","type":"bmw"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];

removeDuplicates(array);

console.log(array);

Answer 2

不删除元素，创建过滤后的数组：

var yourArray = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];

var cache = {}, 
    filteredArray = yourArray.filter(({type}) => type in cache? false: (cache[type] = true));

console.log(filteredArray);

它具有非破坏性，性能更高，更简单，更短。

修改，即使没有现代功能：

var filteredArray = yourArray.filter(function(item){
        return item.type in this? false: (this[item.type] = true);
    }, {/* the cache-object */}); //abusing `this` to pass the cache object

Answer 3

您可以使用对象跟踪数组中已存在的类型，然后只将那些不存在的数组推送到新数组中：

var vehicles = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];
var uniques = [];
var types = {};
for (var i = 0; i < a.length; i++) {
  if (!types[a[i].type]) { uniques.push(a[i]); }
  types[a[i].type] = true;
}
//uniques = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"black","type":"mercedes"}];

检查数组的更多元素是否具有相同的键值，如果它们已删除了一个？

3 个答案: