在Javascript中，有沒有一種方法可以統計我創建了多少個創建的對象？

Question

例如，假設我真的很餓，所以我只是繼續製作煎餅！

var Buttermilk = new Pancake("Buttermilk", "Delicious"); 
var ChocolateChip = new Pancake("Chocolate Chip", "Amazing"); 
var BlueBerry = new Pancake("Blue Berry", "The Best"); 
var SnozBerry = new Pancake("Snoz Berry", "What's a Snoz Berry?"); 

我該如何計算我手動製作的煎餅數量？是否有代碼說「有這麼多變量是煎餅品種」？

編輯：

謝謝你的答案！我專門尋找一種簡單的方法來快速計算我用少量代碼創建對象的次數。這就是我得到的，謝謝！

Answer 1

你可以在JavaScript類中具有靜態屬性。您可以把他們藏在封這樣：

var Pancake = (function() { 
    var instances = 0; 
    return function(a, b) { 
     this.a = a; 
     this.b = b; 
     instances++; 

     Pancake.prototype.instances = function() { // equivalent of a static method 
      return instances; 
     } 
    }; 
}()); 

或把它們放到對象原型：

var pancake = function(a, b) { 
    this.a = a; 
    this.b = b; 
    pancake.prototype.count = pancake.prototype.count ? pancake.prototype.count + 1 : 1; // equivalent of a static property 
} 

你也可以「覆蓋」的構造，通過實施某種「繼承」，如在此琴：

var Pancake = function(a, b) { 
 
\t this.a = a; 
 
    this.b = b; 
 
}; 
 

 
var before = Pancake.prototype; 
 
var Pancake = function() { 
 
\t console.log("overriden"); 
 
\t Pancake.prototype.instances = Pancake.prototype.instances ? Pancake.prototype.instances + 1 : 1; // here you should restore the whole prototype 
 
    return before.constructor.apply(this, arguments); 
 
}; 
 

 

 
var a = new Pancake("a", "b"); 
 
document.write(Pancake.prototype.instances + "<br />"); 
 
var b = new Pancake("c", "d"); 
 
document.write(Pancake.prototype.instances + "<br />"); 
 

 
document.write(JSON.stringify(a) + "<br />"); 
 
document.write(JSON.stringify(b) + "<br />");

Answer 2

使用計數器變量煎餅函數內部.. :)

var count = 0; 
function Pancake(){ 
// Cook pancakes 
count += 1; 
} 

console.log('Total pancakes' + count); 

Answer 3

您可以保留一個計數器，這將在構造函數中得到增量，這裏是一個很好的解決方案

How can I count the instances of an object?

Answer 4

我知道你已經接受了一個答案，但是這花了我一段時間！從你的問題，我想你可能不想改變煎餅班。所以這是爲了避免這種情況。

該函數將搜索您指定的對象中的所有對象並計算您的類型的所有實例。

// Usage: 
    searchObjectForType(window, Pancake); // returns a number. 

    function searchObjectForType(obj,type){ 
     // Keep track of objects in stack so we don't overflow by searching into the same objects; 
     var stackObjs = []; 

     function recursiveProbe(obj){ 
      var foundCount = 0; 
      var objType; 
      // Some types will throw (iframes/nulls/..) 
      try{ 
      objType = obj.toString(); 
      } 
      catch(err){ 
      return 0; 
      } 
      // Skip document/previous objects as we know they won't have any. 
      if(typeof obj === "string" || stackObjs.indexOf(objType)>=0 || obj===document){ 
      return 0; 
      } 
      else{ 
      stackObjs.push(objType); 
      } 

      for (var i in obj){ 
      var prop = obj[i]; 
      if(prop instanceof type){ 
       foundCount++; 
      } 
      else{ 
       foundCount += recursiveProbe(prop); 
      } 
      } 
      // Remove this type from stackObjs so we can search future types. 
      stackObjs.splice(stackObjs.indexOf(obj.toString()),1); 
      return foundCount; 
     } 

     return recursiveProbe(obj); 
    }    

我敢肯定，有些情況下，這失敗了，所以反饋讚賞！