Issue #2990 - implement object.GroupBy

js/src/builtin/Object.cpp

@@ -1247,6 +1247,7 @@ static const JSFunctionSpec object_static_methods[] = {
     JS_FN("seal",                      obj_seal,                    1, 0),
     JS_FN("isSealed",                  obj_isSealed,                1, 0),
     JS_SELF_HOSTED_FN("fromEntries",   "ObjectFromEntries",         1, 0),
+    JS_SELF_HOSTED_FN("groupBy",       "ObjectGroupBy",             2, 0),
     JS_SELF_HOSTED_FN("hasOwn",        "ObjectHasOwn",              2, 0),
     JS_FS_END
 };

js/src/builtin/Object.js

@@ -8,21 +8,22 @@ function ObjectStaticAssign(target, firstSource) {
   var to = ToObject(target);
 
   // Step 3.
-    if (arguments.length < 2)
-        return to;
+  if (arguments.length < 2) return to;
 
   // Steps 4-5.
   for (var i = 1; i < arguments.length; i++) {
     // Step 5.a.
     var nextSource = arguments[i];
-        if (nextSource === null || nextSource === undefined)
-            continue;
+    if (nextSource === null || nextSource === undefined) continue;
 
     // Steps 5.b.i-ii.
     var from = ToObject(nextSource);
 
     // Steps 5.b.iii-iv.
-        var keys = OwnPropertyKeys(from, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS);
+    var keys = OwnPropertyKeys(
+      from,
+      JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS,
+    );
 
     // Step 5.c.
     for (var nextIndex = 0, len = keys.length; nextIndex < len; nextIndex++) {
@@ -47,7 +48,10 @@ function ObjectGetOwnPropertyDescriptors(O) {
   var obj = ToObject(O);
 
   // Step 2.
-    var keys = OwnPropertyKeys(obj, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS);
+  var keys = OwnPropertyKeys(
+    obj,
+    JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS,
+  );
 
   // Step 3.
   var descriptors = {};
@@ -99,15 +103,14 @@ function ObjectDefineSetter(name, setter) {
   var object = ToObject(this);
 
   // Step 2.
-    if (!IsCallable(setter))
-        ThrowTypeError(JSMSG_BAD_GETTER_OR_SETTER, "setter");
+  if (!IsCallable(setter)) ThrowTypeError(JSMSG_BAD_GETTER_OR_SETTER, "setter");
 
   // Step 3.
   var desc = {
     __proto__: null,
     enumerable: true,
     configurable: true,
-        set: setter
+    set: setter,
   };
 
   // Step 4.
@@ -125,15 +128,14 @@ function ObjectDefineGetter(name, getter) {
   var object = ToObject(this);
 
   // Step 2.
-    if (!IsCallable(getter))
-        ThrowTypeError(JSMSG_BAD_GETTER_OR_SETTER, "getter");
+  if (!IsCallable(getter)) ThrowTypeError(JSMSG_BAD_GETTER_OR_SETTER, "getter");
 
   // Step 3.
   var desc = {
     __proto__: null,
     enumerable: true,
     configurable: true,
-        get: getter
+    get: getter,
   };
 
   // Step 4.
@@ -151,7 +153,7 @@ function ObjectLookupSetter(name) {
   var object = ToObject(this);
 
   // Step 2.
-    var key = ToPropertyKey(name)
+  var key = ToPropertyKey(name);
 
   do {
     // Step 3.a.
@@ -160,8 +162,7 @@ function ObjectLookupSetter(name) {
     // Step 3.b.
     if (desc) {
       // Step.b.i.
-            if (callFunction(std_Object_hasOwnProperty, desc, "set"))
-                return desc.set;
+      if (callFunction(std_Object_hasOwnProperty, desc, "set")) return desc.set;
 
       // Step.b.ii.
       return undefined;
@@ -180,7 +181,7 @@ function ObjectLookupGetter(name) {
   var object = ToObject(this);
 
   // Step 2.
-    var key = ToPropertyKey(name)
+  var key = ToPropertyKey(name);
 
   do {
     // Step 3.a.
@@ -189,8 +190,7 @@ function ObjectLookupGetter(name) {
     // Step 3.b.
     if (desc) {
       // Step.b.i.
-            if (callFunction(std_Object_hasOwnProperty, desc, "get"))
-                return desc.get;
+      if (callFunction(std_Object_hasOwnProperty, desc, "get")) return desc.get;
 
       // Step.b.ii.
       return undefined;
@@ -221,6 +221,46 @@ function ObjectFromEntries(iter) {
   return obj;
 }
 
+// ES2024
+// Object.groupBy ( items, callbackfn )
+function ObjectGroupBy(items, callbackfn) {
+  // Step 1.
+  RequireObjectCoercible(items);
+
+  // Step 2.
+  if (!IsCallable(callbackfn))
+    ThrowTypeError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
+
+  // Step 3.
+  var groups = std_Object_create(null);
+
+  // Step 4.
+  var k = 0;
+
+  // Steps 5-8.
+  for (var value of allowContentIter(items)) {
+    // Step 6.a.
+    var key = callContentFunction(callbackfn, undefined, value, k);
+
+    // Step 6.b.
+    key = ToPropertyKey(key);
+
+    // Steps 6.c-d.
+    var elements = groups[key];
+    if (elements === undefined) {
+      _DefineDataProperty(groups, key, [value]);
+    } else {
+      callFunction(std_Array_push, elements, value);
+    }
+
+    // Step 6.e.
+    k++;
+  }
+
+  // Step 9.
+  return groups;
+}
+
 // Proposal https://github.com/tc39/proposal-accessible-object-hasownproperty
 // Object.hasOwn (Object, Property)
 function ObjectHasOwn(O, P) {

js/src/tests/ecma_6/Object/groupBy.js

@@ -0,0 +1,89 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+assertEq(typeof Object.groupBy, "function");
+assertEq(Object.groupBy.length, 2);
+
+let desc = Object.getOwnPropertyDescriptor(Object, "groupBy");
+assertEq(desc.enumerable, false);
+assertEq(desc.writable, true);
+assertEq(desc.configurable, true);
+
+{
+    let values = [1, 2, 3, 4, 5];
+    let calls = [];
+
+    let grouped = Object.groupBy(values, function (value, index) {
+        "use strict";
+        assertEq(this, undefined);
+        calls.push([value, index]);
+        return value % 2 ? "odd" : "even";
+    });
+
+    assertEq(Object.getPrototypeOf(grouped), null);
+    assertDeepEq(Object.keys(grouped), ["odd", "even"]);
+    assertDeepEq(grouped.odd, [1, 3, 5]);
+    assertDeepEq(grouped.even, [2, 4]);
+    assertDeepEq(calls, [[1, 0], [2, 1], [3, 2], [4, 3], [5, 4]]);
+}
+
+{
+    let sym = Symbol("key");
+    let grouped = Object.groupBy([10, 11], value => value === 10 ? sym : 0);
+
+    assertDeepEq(Object.keys(grouped), ["0"]);
+    assertDeepEq(grouped[0], [11]);
+
+    let symbols = Object.getOwnPropertySymbols(grouped);
+    assertEq(symbols.length, 1);
+    assertEq(symbols[0], sym);
+    assertDeepEq(grouped[sym], [10]);
+}
+
+{
+    let grouped = Object.groupBy([1, 2], () => "__proto__");
+    assertEq(Object.getPrototypeOf(grouped), null);
+    assertDeepEq(grouped["__proto__"], [1, 2]);
+
+    let protoKeyDesc = Object.getOwnPropertyDescriptor(grouped, "__proto__");
+    assertEq(protoKeyDesc.enumerable, true);
+    assertEq(protoKeyDesc.writable, true);
+    assertEq(protoKeyDesc.configurable, true);
+}
+
+{
+    let closed = false;
+    let iterable = {
+        [Symbol.iterator]() {
+            let i = 0;
+            return {
+                next() {
+                    i++;
+                    if (i <= 3)
+                        return { value: i, done: false };
+                    return { done: true };
+                },
+                return() {
+                    closed = true;
+                    return { done: true };
+                }
+            };
+        }
+    };
+
+    assertThrowsValue(() => Object.groupBy(iterable, value => {
+        if (value === 2)
+            throw 42;
+        return "x";
+    }), 42);
+    assertEq(closed, true);
+}
+
+assertThrowsInstanceOf(() => Object.groupBy([], null), TypeError);
+assertThrowsInstanceOf(() => Object.groupBy(null, null), TypeError);
+assertThrowsInstanceOf(() => Object.groupBy({}, x => x), TypeError);
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);