Refactor Iterator implementation for better maintainability

Added helper methods to reduce code duplication:
- getNextMethod(): Extract and validate next method
- callNext(): Call next and validate result
- isDone(): Check if iteration is complete
- getValue(): Extract value from result object
- closeIterator(): Close iterator via return() method

Removed redundant inline comments that duplicated method names.
Consolidated repetitive iterator protocol validation.

No functional changes - purely code quality improvements.

Author: anivar

rhino/src/main/java/org/mozilla/javascript/NativeES2025Iterator.java

@@ -6,18 +6,12 @@
 
 package org.mozilla.javascript;
 
-/**
- * Implementation of the ES2025 Iterator constructor and Iterator.prototype. This provides the
- * Iterator constructor function and static methods like Iterator.from.
- */
+/** ES2025 Iterator constructor and helper methods. */
 public class NativeES2025Iterator extends ScriptableObject {
     private static final long serialVersionUID = 1L;
-
     private static final String CLASS_NAME = "Iterator";
 
     static void init(Context cx, ScriptableObject scope, boolean sealed) {
-        // Create Lambda constructor
-        // Iterator constructor throws TypeError when called
         LambdaConstructor constructor =
                 new LambdaConstructor(
                         scope,
@@ -26,22 +20,18 @@ static void init(Context cx, ScriptableObject scope, boolean sealed) {
                         LambdaConstructor.CONSTRUCTOR_FUNCTION,
                         NativeES2025Iterator::constructor);
 
-        // Define static methods on constructor
         constructor.defineConstructorMethod(
                 scope, "from", 1, NativeES2025Iterator::js_from, DONTENUM);
         constructor.defineConstructorMethod(
                 scope, "concat", 0, NativeES2025Iterator::js_concat, DONTENUM);
 
-        // Define prototype methods
         constructor.definePrototypeMethod(
                 scope,
                 SymbolKey.ITERATOR,
                 0,
                 NativeES2025Iterator::js_iterator,
                 DONTENUM,
                 DONTENUM);
-
-        // Iterator helper methods
         constructor.definePrototypeMethod(
                 scope, "map", 1, NativeES2025Iterator::js_map, DONTENUM, DONTENUM);
         constructor.definePrototypeMethod(
@@ -65,7 +55,6 @@ static void init(Context cx, ScriptableObject scope, boolean sealed) {
         constructor.definePrototypeMethod(
                 scope, "find", 1, NativeES2025Iterator::js_find, DONTENUM, DONTENUM);
 
-        // Define Symbol.toStringTag as a value property on prototype
         constructor.definePrototypeProperty(
                 SymbolKey.TO_STRING_TAG, CLASS_NAME, DONTENUM | READONLY);
 
@@ -84,46 +73,33 @@ public String getClassName() {
         return CLASS_NAME;
     }
 
-    // Lambda-based method implementations
-
     private static Scriptable constructor(Context cx, Scriptable scope, Object[] args) {
-        // ES2025 Iterator constructor throws TypeError when called
         throw ScriptRuntime.typeError("Iterator is not a constructor");
     }
 
     private static Object js_iterator(
             Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
-        // Symbol.iterator returns this
         return thisObj;
     }
 
     private static Object js_from(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
-        // Iterator.from(item) implementation
-        // If item is already an iterator with proper prototype, return it
-        // Otherwise wrap it in an iterator
-
         Object item = args.length > 0 ? args[0] : Undefined.instance;
 
         if (item == null || item == Undefined.instance) {
             throw ScriptRuntime.typeError("Cannot convert undefined or null to iterator");
         }
 
-        // Check if it's already an iterator that inherits from Iterator.prototype
         if (item instanceof ES2025IteratorPrototype) {
             return item;
         }
 
-        // Check for Symbol.iterator method
         if (item instanceof Scriptable) {
             Scriptable scriptable = (Scriptable) item;
             Object iteratorMethod = ScriptableObject.getProperty(scriptable, SymbolKey.ITERATOR);
 
             if (iteratorMethod != Scriptable.NOT_FOUND && iteratorMethod instanceof Callable) {
-                // Call @@iterator to get iterator
                 Callable callable = (Callable) iteratorMethod;
                 Object iterator = callable.call(cx, scope, scriptable, ScriptRuntime.emptyArgs);
-
-                // Wrap the iterator to inherit from Iterator.prototype
                 return new WrappedIterator(cx, scope, iterator);
             }
         }
@@ -133,22 +109,17 @@ private static Object js_from(Context cx, Scriptable scope, Scriptable thisObj,
 
     private static Object js_concat(
             Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
-        // Iterator.concat(...items) implementation
-        // Validate and collect iterables
         Scriptable[] iterables = new Scriptable[args.length];
         Callable[] iteratorMethods = new Callable[args.length];
 
         for (int i = 0; i < args.length; i++) {
             Object item = args[i];
 
-            // Each item must be an object
             if (!(item instanceof Scriptable)) {
                 throw ScriptRuntime.typeError("Iterator.concat requires iterable objects");
             }
 
             Scriptable itemObj = (Scriptable) item;
-
-            // Get the Symbol.iterator method
             Object iteratorMethod = ScriptableObject.getProperty(itemObj, SymbolKey.ITERATOR);
 
             if (!(iteratorMethod instanceof Callable)) {
@@ -163,35 +134,51 @@ private static Object js_concat(
         return new ConcatIterator(cx, scope, iterables, iteratorMethods);
     }
 
-    // Iterator.prototype.toArray()
-    private static Object js_toArray(
-            Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
-        // Get the iterator's next method
-        Object next = ScriptableObject.getProperty(thisObj, "next");
+    private static Callable getNextMethod(Scriptable iterator) {
+        Object next = ScriptableObject.getProperty(iterator, "next");
         if (!(next instanceof Callable)) {
             throw ScriptRuntime.typeError("Iterator must have a next method");
         }
-        Callable nextMethod = (Callable) next;
+        return (Callable) next;
+    }
+
+    private static Scriptable callNext(
+            Context cx, Scriptable scope, Scriptable thisObj, Callable nextMethod) {
+        Object result = nextMethod.call(cx, scope, thisObj, ScriptRuntime.emptyArgs);
+        if (!(result instanceof Scriptable)) {
+            throw ScriptRuntime.typeError("Iterator result must be an object");
+        }
+        return (Scriptable) result;
+    }
+
+    private static boolean isDone(Scriptable result) {
+        Object done = ScriptableObject.getProperty(result, "done");
+        return ScriptRuntime.toBoolean(done);
+    }
 
-        // Create array to collect values
+    private static Object getValue(Scriptable result) {
+        return ScriptableObject.getProperty(result, "value");
+    }
+
+    private static void closeIterator(Context cx, Scriptable scope, Scriptable iterator) {
+        Object returnMethod = ScriptableObject.getProperty(iterator, "return");
+        if (returnMethod instanceof Callable) {
+            ((Callable) returnMethod).call(cx, scope, iterator, ScriptRuntime.emptyArgs);
+        }
+    }
+
+    private static Object js_toArray(
+            Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
+        Callable nextMethod = getNextMethod(thisObj);
         Scriptable array = cx.newArray(scope, 0);
         int index = 0;
 
-        // Iterate and collect all values
         while (true) {
-            Object result = nextMethod.call(cx, scope, thisObj, ScriptRuntime.emptyArgs);
-            if (!(result instanceof Scriptable)) {
-                throw ScriptRuntime.typeError("Iterator result must be an object");
-            }
-            Scriptable resultObj = (Scriptable) result;
-
-            Object done = ScriptableObject.getProperty(resultObj, "done");
-            if (ScriptRuntime.toBoolean(done)) {
+            Scriptable result = callNext(cx, scope, thisObj, nextMethod);
+            if (isDone(result)) {
                 break;
             }
-
-            Object value = ScriptableObject.getProperty(resultObj, "value");
-            array.put(index++, array, value);
+            array.put(index++, array, getValue(result));
         }
 
         return array;