Javascript单例，如何更新这个变量？

Question

快速提问。假设我有这个对象：

var door = (function(){
    var state = "closed";

    function doSomething(){
      //do something here
      state = "open";
    }

    return {
        activate: function() {
           doSomething();
        },
        doorState: state
    }
})();

现在，如果我这样做：door.activate() door.doorState 是 "closed"。我可以这样做：

doorState: function(){state}

但这需要我做 door.doorState()

我希望能够更新对象的状态而不是调用函数。

如何？

Answer 1

问题是你只是更新局部变量，但它不会更新 doorState 属性

的值

您可以更新返回对象的属性

var door = (function() {

  function doSomething() {
    //do something here
    obj.doorState = "open";
  }

  var obj = {
    activate: function() {
      doSomething();
    },
    doorState: "closed"
  }
  return obj;
})();

snippet.log('before: ' + door.doorState);
door.activate();
snippet.log('after: ' + door.doorState);

<!-- Provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

使用getter syntax - supported in IE9+

var door = (function() {
  var door = 'closed';

  function doSomething() {
    //do something here
    door = "open";
  }

  return {
    activate: function() {
      doSomething();
    },
    get doorState() {
      return door;
    }
  }
})();

snippet.log('before: ' + door.doorState);
door.activate();
snippet.log('after: ' + door.doorState);

<!-- Provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

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