JavaScript的單例模式（singleton in Javascript)

2019-11-21 00:26:13

字體：大中小

供稿：網(wǎng)友

單例模式的基本結(jié)構(gòu)：

 
MyNamespace.Singleton = function() { 
return {}; 
}(); 

比如：

復(fù)制代碼代碼如下:

 
MyNamespace.Singleton = (function() { 
return { // Public members. 
publicAttribute1: true, 
publicAttribute2: 10, 
publicMethod1: function() { 
... 
}, 
publicMethod2: function(args) { 
... 
} 
}; 
})(); 

但是，上面的Singleton在代碼一加載的時候就已經(jīng)建立了，怎么延遲加載呢？想象C#里怎么實現(xiàn)單例的:)采用下面這種模式：

復(fù)制代碼代碼如下:

 
MyNamespace.Singleton = (function() { 
function constructor() { // All of the normal singleton code goes here. 
... 
} 
return { 
getInstance: function() { 
// Control code goes here. 
} 
} 
})(); 

具體來說，把創(chuàng)建單例的代碼放到constructor里，在首次調(diào)用的時候再實例化：
完整的代碼如下：

復(fù)制代碼代碼如下:

 
MyNamespace.Singleton = (function() { 
var uniqueInstance; // Private attribute that holds the single instance. 
function constructor() { // All of the normal singleton code goes here. 
... 
} 
return { 
getInstance: function() { 
if(!uniqueInstance) { // Instantiate only if the instance doesn't exist. 
uniqueInstance = constructor(); 
} 
return uniqueInstance; 
} 
} 
})(); 