Javascript and referencing one namespace property from another [duplicate]

问题

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Closed 6 years ago.

Possible Duplicate:
How can a Javascript object refer to values in itself?

Let's say I have:

var myNamespace = {
      _prop1: 'hello',
      _prop2: _prop1 + ' you!'
};

I'm just now finding out that this will error on _prop2 at load.

I can't understand why this doesn't work, I've worked around it in my code but I would still like to understand.

回答1:

When you try and set prop2 the object hasn't initialised so the value of prop1 and mynamespace are both undefined.

There are a couple of ways to achieve what you want, one way would be to create prop2 as a function so it can dynamically get the value of prop1

var myNamespace = {
      _prop1: 'hello',
      _prop2: function(){ return this._prop1 + ' you!' }
};

Another way would be to set prop2 after myNamespace has been initialised

回答2:

You have to use this:

var myNamespace = {
    _prop1: 'hello'
};
myNamespace._prop2: myNamespace._prop1 + ' you!';

回答3:

Well, you can do

var myNamespace = {
      _prop1: 'hello',
      _prop2: myNamespace._prop1 + ' you!'
};

I don't think it's possible to do it any other way in the declaration (eg: using "self" or "this" doesn't work)

来源：https://stackoverflow.com/questions/14553639/javascript-and-referencing-one-namespace-property-from-another