如何正确定位这种"公共"方法？

Question

我有这个代码(JSFiddle)

var OBJ = function(){
    var privateVar = 23;
    var self = this;

    return {
        thePrivateVar : function() {
          return privateVar;
        },  

        thePrivateVarTimeout : function() {
            setTimeout(function() { alert(self.thePrivateVar()); } , 10);
        }
    }

}();

alert(OBJ.thePrivateVar());

OBJ.thePrivateVarTimeout();

这是我正在遇到的一个真正问题的抽象.

所以 - 我希望调用OBJ.thePrivateVarTimeout()等待10然后alert使用23(我希望它通过其他公开的方法访问).

但self似乎没有正确设置.当我设置self = this它时,它似乎this不是对函数的引用,而是对全局对象的引用.为什么是这样？

如何让public方法thePrivateVarTimeout调用其他公共方法thePrivateVar？

Answer 1

var OBJ = (function(){
    var privateVar = 23;
    var self = {
        thePrivateVar : function() {
          return privateVar;
        },  

        thePrivateVarTimeout : function() {
            setTimeout(function() { alert(self.thePrivateVar); } , 10);
        }
    };

    return self;

}());

this === global || undefined在一个被调用的函数里面.在ES5中,无论全局环境如何,在ES5严格中它都是未定义的.

更常见的模式将涉及var that = this在函数中使用作为局部值

var obj = (function() {
  var obj = {
    property: "foobar",
    timeout: function _timeout() {
      var that = this;
      setTimeout(alertData, 10);

      function alertData() {
        alert(that.property);
      }
    }
  }

  return obj;
}());

或使用.bindAll方法

var obj = (function() {
  var obj = {
    alertData: function _alertData() {
      alert(this.property);
    }
    property: "foobar",
    timeout: function _timeout() {
      setTimeout(this.alertData, 10);
    }
  }

  bindAll(obj)

  return obj;
}());


/*
    bindAll binds all methods to have their context set to the object

    @param Object obj - the object to bind methods on
    @param Array methods - optional whitelist of methods to bind

    @return Object - the bound object
*/
function bindAll(obj, whitelist) {
    var keys = Object.keys(obj).filter(stripNonMethods);

    (whitelist || keys).forEach(bindMethod);

    function stripNonMethods(name) {
        return typeof obj[name] === "function";
    }

    function bindMethod(name) {
        obj[name] = obj[name].bind(obj);
    }

    return obj;
}