Behavior of Object.bindProperties() Method of Nashorn

[A. Sundararajan]

And I expanded wiki page section on bindProperties after your question :-)

https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions#Nashornextensions-Object.bindProperties

Thanks
-Sundar

On Thursday 16 October 2014 09:25 PM, A. Sundararajan wrote:
> Object.bindProperties considers properties at the time of bindings 
> only. No "tracking" of object after it is bound. Also, only properties 
> that don't exist in target object are bound from source (again check 
> is at the time of binding).
>
> Hope this helps,
> -Sundar
>
> On Friday 10 October 2014 11:08 PM, Kishori Sharan wrote:
>> Hello Everyone,
>>
>> I was experimenting with the Object.bindProperties() method in 
>> Nashorn and
>> found a few weird behaviors. I would like to ask two questions:
>> 1. Is there a comprehensive documentation for this method, except at
>> https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions#Nashornextensions-loadWithNewGlobal 
>>
>> 2. Is it a bug as explained in the following snippet of code?
>>
>> The following code does not bind the x, y, and z properties of obj2 
>> to obj
>> because obj already has properties with the same names. Is it documented
>> somewhere?
>>
>> var obj = {x:10, y:20, z:30};
>>
>> var obj2 = {x:100, y:200, z:300};
>>
>>
>>
>> // bind properties of 'obj2' to 'obj'
>>
>> Object.bindProperties(obj, obj2);
>>
>>
>>
>> print(obj.x, obj.y, obj.z);
>>
>> print(obj2.x, obj2.y, obj2.z);
>>
>> ---------------------------------
>>
>> 10 20 30
>>
>> 100 200 300
>>
>> --------------------------------
>>
>> Now, let us add a new property to obj2. The new property is bound to 
>> obj,
>> but obj reads the new property's value as null:
>>
>> var obj = {x:10, y:20, z:30};
>>
>> var obj2 = {x:100, y:200, z:300};
>>
>>
>>
>> // Add a new property to obj2
>>
>> obj2.u = 600;
>>
>>
>>
>> // bind properties of 'obj2' to 'obj'
>>
>> Object.bindProperties(obj, obj2);
>>
>>
>>
>> print(obj.x, obj.y, obj.z, obj.u);  // obj.u is null. Why?
>>
>> print(obj2.x, obj2.y, obj2.z, obj2.u);
>>
>>
>>
>> ---------------------------------
>>
>> 10 20 30 null
>>
>> 100 200 300 600
>>
>> --------------------------------
>>
>> And, here is another variant of the code that works. This time, I 
>> started
>> the target object as empty. Now, adding the new property to the source
>> works fine.
>>
>> var obj = {};
>>
>> var obj2 = {x:100, y:200, z:300};
>>
>>
>>
>> // Add a new property to obj2
>>
>> obj2.u = 600;
>>
>>
>>
>> // bind properties of 'obj2' to 'obj'
>>
>> Object.bindProperties(obj, obj2);
>>
>>
>>
>> print(obj.x, obj.y, obj.z, obj.u);  // obj.u is correct.It is 600
>>
>> print(obj2.x, obj2.y, obj2.z, obj2.u);
>>
>>
>>
>> ----------------------------
>>
>> 100 200 300 600
>>
>> 100 200 300 600
>>
>> ----------------------------
>>
>> I am using JDK version 1.8.0_20.
>> Thanks
>> Kishori
>