Javascript“this”scope

Question

我在写一些JavaScript代码。我对这个关键词有点困惑。如何访问dataReceivedHandler函数中的记录器变量？

MyClass: { 
    logger: null, 
    init: function() { 
     logger = LogFactory.getLogger(); 
    }, 
    loadData: function() { 
     var dataReceivedHandler = function() { 
      // how to access the logger variable here? 
     } 

     // more stuff 
    } 
}; 

Answer 1

假设loadData被称为像这样：

MyClass.loadData(); 

则：

loadData: function() { 
    var self = this; 
    var dataReceivedHandler = function() { 
     self.logger ... 
    } 

    // more stuff 
} 

Answer 2

你可以这样做的loadData函数里面的东西访问你的对象......

MyClass: { 
    logger: null, 
    init: function() { 
     this.logger = LogFactory.getLogger(); 
    }, 
    loadData: function() { 
     var self = this; 
     var dataReceivedHandler = function() { 
      // how to access the logger variable here? 
      self.logger.log('something'); 
     } 

     // more stuff 
    } 
}; 

Answer 3

Becaus e dataReceivedHandler是一个匿名函数，this将引用全局作用域上的窗口对象。我想你可以绕过这两条路。

一）内部loadData创建一个变量来保存它的上下文然后用它里面dataReceivedHandler这样：

loadData: function() { 
    var self = this; 
    var dataReceivedHandler = function() { 
     console.log(self.logger); 
    } 

    // more stuff 
} 

b）使用apply或call更改匿名函数的上下文。

loadData: function() { 
    var dataReceivedHandler = function() { 
     console.log(this.logger); 
    } 
    // more stuff 
    dataReceivedHandler.call(this); // by passing this as the first argument we make sure the context of the excuted function is our current scope's this 
} 

由于性能和内存使用优化，我更喜欢选项B，但两者都可以正常工作。