Intercept the fetching of properties / methods of a javascript object
<p>How/Can I intercept a request to get a method/property on an javascript object and return a custom value instead.</p>

<p>For example,</p>

<pre><code>var obj = {
    // This "get" method is where I want to replace the call to get a property of an object.
    get : function(propertyName) {
        if (propertyName == 'somePropertyThatDoesntExist') { return 1; }
        else { return 0; } // Something like this?
};

// Either this method of access,
var myValue1 = obj.somePropertyThatDoesntExist
var myValue2 = obj.someOtherPropertyThatDoesntExist

// Alternatively, 
var myValue3 = obj['somePropertyThatDoesntExist']
var myValue4 = obj['someOtherPropertyThatDoesntExist']
</code></pre>

<p>So myValue1 and myValue3 will have a value of 1, and myValue2 and myValue4 will have a value of 0.</p>

<p>Currently, myValue1, 2, 3, 4 would all be "undefined".</p>
