javascript - 如何在 Javascript 中访问外部对象上的函数

Question

我无法在 FB.api 中调用 method()。我怎样才能访问方法？ 做不到 this.method();或方法();

var MyLayer = cc.Layer.extend({
   init: function(){
      FB.init({
       ............
      });
      FB.getLoginStatus(function(response) {
         if (response.status === 'connected') {
               FB.api('/me', function(response) {
                  this.method(); // <---- I cant call this here. How can I call method(); ?? Thank!
               });
         }
      });
   },
   method: function(){
      alert("Hello");
   }
});

Answer 1

保存对 this 的引用并使用它:

var MyLayer = cc.Layer.extend({
   init: function(){
       var that = this; // Save reference to context
       //.....
       FB.getLoginStatus(function(response) {
           if (response.status === 'connected') {
               FB.api('/me', function(response) {
                  that.method(); // Call method on stored context
               });
           }
        });
    }
});

或者您可以 bind上下文的回调函数(需要 ES5):

var MyLayer = cc.Layer.extend({
   init: function(){
       //.....
       FB.getLoginStatus(function(response) {
           if (response.status === 'connected') {
               FB.api('/me', function(response) {
                  this.method(); // Call method on context
               }.bind(this)); // Bind callback to context
           }
        }.bind(this)); // Bind callback to context
    }
});