Help re. my first exercise in Rhino

[Hariharan Karuppasamy]

Hi all,

I am working on this task:

https://github.com/mozilla/rhino/issues/1307

I am starting with the toReversed method. I understand the change should go in NativeArray.java

This is the algorithm that I got. How do I find the equivalent Java methods to implement this logic? I appreciate your inputs to how go with this implementation.

When the toReversed method is called, the following steps are taken:

1. 1. Let O be ? ToObject(this value).
2. 2. Let len be ? LengthOfArrayLike(O).
3. 3. Let A be ? ArrayCreate(𝔽(len)).
4. 4. Let k be 0.
5. 5. Repeat, while k < len,
   1. a. Let from be ! ToString(𝔽(len - k - 1)).
   2. b. Let Pk be ! ToString(𝔽(k)).
   3. c. Let fromValue be ? Get(O, from).
   4. d. Perform ! CreateDataPropertyOrThrow(A, Pk, fromValue).
   5. e. Set k to k + 1.
6. 6. Return A.

[P]

Hi,

There are no clear-cut answers here. Best approach I find is to look at prior implementations of similar stuff, like for example the implementation of the .at(idx) method, see https://github.com/mozilla/rhino/pull/1289

[Hariharan Karuppasamy]

Yes, I did have a look around. Thanks for this. Can I submit one PR after the toReveresed() implementation before I carry on with other methods?

[P]

Maybe create a draft PR for feedback once you have toReversed implemented, while you continue to work on the other methods?

[Hariharan Karuppasamy]

Hi, 

I have checked in the code to this branch "hari-change-array-by-copy" . However I get the below error when testing the method manually from the console. I don't see NativeArray invoked in the exception stack trace. What's going wrong in the code? Any ideas please

js> const items = [1, 2, 3];
js> items
1,2,3
js> items.toReversed()
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 70 out of bounds for length 70
        at org.mozilla.javascript.IdScriptableObject$PrototypeValues.ensureId(IdScriptableObject.java:284)
        at org.mozilla.javascript.IdScriptableObject$PrototypeValues.get(IdScriptableObject.java:162)
        at org.mozilla.javascript.IdScriptableObject.get(IdScriptableObject.java:380)
        at org.mozilla.javascript.ScriptableObject.getProperty(ScriptableObject.java:2037)
        at org.mozilla.javascript.ScriptRuntime.getPropFunctionAndThisHelper(ScriptRuntime.java:2584)
        at org.mozilla.javascript.ScriptRuntime.getPropFunctionAndThis(ScriptRuntime.java:2575)
        at org.mozilla.javascript.optimizer.OptRuntime.callProp0(OptRuntime.java:71)
        at org.mozilla.javascript.gen._stdin__3._c_script_0(<stdin>:4)
        at org.mozilla.javascript.gen._stdin__3.call(<stdin>)
        at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:383)
        at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3876)
        at org.mozilla.javascript.gen._stdin__3.call(<stdin>)
        at org.mozilla.javascript.gen._stdin__3.exec(<stdin>)
        at org.mozilla.javascript.tools.shell.Main.processSource(Main.java:482)
        at org.mozilla.javascript.tools.shell.Main.processFiles(Main.java:180)
        at org.mozilla.javascript.tools.shell.Main$IProxy.run(Main.java:98)
        at org.mozilla.javascript.Context.call(Context.java:544)
        at org.mozilla.javascript.ContextFactory.call(ContextFactory.java:475)
        at org.mozilla.javascript.tools.shell.Main.exec(Main.java:164)
        at org.mozilla.javascript.tools.shell.Main.main(Main.java:142)

[Hariharan Karuppasamy]

Done, created a draft PR with the query above. Thanks