訪問JavaScript類的靜態屬性而不使用類的實例

Question

我試圖訪問一個類的靜態屬性，而不使用該類的實例來這樣做。我試圖修改this post中的方法，但無濟於事。我得到的全部是test.getInstanceId is not a function

根據我如何創建類（如下），我該怎麼做？ Here is a fiddle。

test = (function() { 
    var currentInstance; 

    function test() { 
    this.id = 0; 
    currentInstance = this; 
    // this won 't work 
    this.getInstanceId = function() { 
     return currentInstance.id; 
    } 
    } 


    test.prototype.setId = function(id) { 
    this.id = id; 
    } 

    return test; 
})(); 


var myTest = new test(); 
myTest.setId(1); 
console.log(myTest.id) 
console.log(test.getInstanceId()); 

Answer 1

感謝RobG，以下作品的代碼。它通過使用test.currentInstance = ...將變量設置爲公開。這裏是the working fiddle。

當檢查對象test時，現在的公共變量currentInstance似乎「活」在test函數原型之外，我沒有意識到這是可能的。

我有不是更正了他指出的命名約定 - 應該是測試而不是測試。

test = (function() { 
    test.currentInstance = undefined; 

    function test() { 
    this.id = 0; 
    test.currentInstance = this; 
    } 


    test.prototype.setId = function(id) { 
    this.id = id; 
    } 

    return test; 
})(); 



var myTest = new test(); 
myTest.setId(1); 
console.log(myTest.id) 
console.log(test.currentInstance.id); 

Answer 2

由於我的意見建議，您正在使用的test.getInstanceId()代替myTest.getInstanceId()

var test = (function() { 
    var currentInstance; 
    /* This won't work 
    function getInstanceId(){ 
     return currentInstance.id; 
    } 
    */ 

    function test() { 
    this.id = 0; 
    currentInstance = this; 
    // this won 't work 
    this.getInstanceId = function() { 
     return currentInstance.id; 
    } 
    } 


    test.prototype.setId = function(id) { 
    this.id = id; 
    } 

    return test; 
})(); 


var myTest = new test(); 
myTest.setId(1); 
console.log(myTest.id) 
console.log(myTest.getInstanceId()); 

Fid的：https://jsfiddle.net/gt0wd8hp/10/