Implement Array.prototype.find and Array.prototype.findIndex in JS

Summary: Implement `Array.prototype.find` and `Array.prototype.findIndex` in JS

Reviewed By: dulinriley

Differential Revision: D17637660

fbshipit-source-id: 0e5ae8e5dd847e19acd6d8f76b83ed55637f6e9e

include/hermes/VM/NativeFunctions.def

@@ -40,7 +40,6 @@ NATIVE_FUNCTION(arrayIteratorPrototypeNext)
 NATIVE_FUNCTION(arrayOf)
 NATIVE_FUNCTION(arrayPrototypeConcat)
 NATIVE_FUNCTION(arrayPrototypeCopyWithin)
-NATIVE_FUNCTION(arrayPrototypeFind)
 NATIVE_FUNCTION(arrayPrototypeForEach)
 NATIVE_FUNCTION(arrayPrototypeIncludes)
 NATIVE_FUNCTION(arrayPrototypeIterator)
@@ -61,6 +60,7 @@ NATIVE_FUNCTION(arrayPrototypeUnshift)
 NATIVE_FUNCTION(arrayPrototypeEvery)
 NATIVE_FUNCTION(arrayPrototypeFill)
 NATIVE_FUNCTION(arrayPrototypeFilter)
+NATIVE_FUNCTION(arrayPrototypeFind)
 NATIVE_FUNCTION(arrayPrototypeIndexOf)
 NATIVE_FUNCTION(arrayPrototypeLastIndexOf)
 NATIVE_FUNCTION(arrayPrototypeMap)

lib/InternalBytecode/Array.js

@@ -471,6 +471,102 @@ Array.prototype.filter = function filter(callbackfn, thisArg = undefined) {
   return A;
 }
 
+/**
+ * Helper function for Array.prototype.find and Array.prototypr.findIndex,
+ * see their doc-comments for more details.
+ * @param arr an array-like value.
+ * @param predicate function to be invoked on the elements.
+ * @param thisArg parameter which will be used as the <this> value
+ *                for each invocation of predicate.
+ * @param returnElement boolean flag for whether to return the element found
+ *                      or index of the element
+ * @return if returnElement is true, returns the first element which makes
+ *         the predicate return a truthy value, and undefined if no such
+ *         element exists.
+ *         If returnElement is false, return index of the first element which
+ *         makes the predicate return a truthy value, and -1 if no such
+ *         element exists.
+ * @throw TypeError if predicate is not a function
+ */
+function arrayPrototypeFindHelper(arr, predicate, thisArg, returnElement) {
+  // Array.prototype.find and Array.prototype.findIndex cannot be used as constructors
+  if (new.target) throw _TypeError('This function cannot be used as a constructor.');
+
+  // 1. Let O be ? ToObject(this value).
+  var O = HermesInternal.toObject(arr);
+  // 2. Let len be ? ToLength(? Get(O, "length")).
+  var len = HermesInternal.toLength(O.length);
+
+  // 3. If IsCallable(predicate) is false, throw a TypeError exception.
+  if (typeof predicate !== 'function') {
+    throw _TypeError('Find argument must be a function');
+  }
+
+  // 4. If thisArg is present, let T be thisArg; else let T be undefined.
+
+  // 5. Let k be 0.
+  var k = 0;
+
+  // fast path which calls the function directly when thisArg is undefined
+  if (thisArg === undefined) {
+    while (k < len) {
+      var kValue = O[k];
+      if (predicate(kValue, k, O)) return returnElement ? kValue : k;
+      k += 1;
+    }
+    return returnElement ? undefined : -1;
+  }
+
+  // 6. Repeat, while k < len
+  while (k < len) {
+    // a. Let Pk be ! ToString(k).
+    // b. Let kValue be ? Get(O, Pk).
+    var kValue = O[k];
+    // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
+    // d. If testResult is true, return kValue. (Array.prototype.find)
+    // d. If testResult is true, return k. (Array.prototype.findIndex)
+    if (HermesInternal.executeCall(predicate, thisArg, kValue, k, O)) {
+      return returnElement ? kValue : k;
+    }
+    // e. Increase k by 1.
+    k += 1;
+  }
+
+  // 7. Return undefined. (Array.prototype.find)
+  // 7. Return -1. (Array.prototype.findIndex)
+  return returnElement ? undefined : -1;
+}
+
+/**
+ * ES10.0 22.1.3.8
+ * Invoke a predicate function on elements in an array-like object until
+ * a return value is truthy or there's no more elments.
+ * @this an array-like value.
+ * @param predicate function to be invoked on the elements.
+ * @param [thisArg] optional parameter which will be used as the <this> value
+ *                  for each invocation of predicate.
+ * @return the first element which makes the predicate return a truthy value,
+ *         and undefined if no such element exists
+ */
+Array.prototype.find = function find(predicate, thisArg = undefined) {
+  return arrayPrototypeFindHelper(this, predicate, thisArg, true);
+}
+
+/**
+ * ES10.0 22.1.3.9
+ * Invoke a predicate function on elements in an array-like object until
+ * a return value is truthy or there's no more elments.
+ * @this an array-like value.
+ * @param predicate function to be invoked on the elements.
+ * @param [thisArg] optional parameter which will be used as the <this> value
+ *                  for each invocation of predicate.
+ * @return index of the first element which makes the predicate return a
+ *         truthy value, and -1 if no such element exists
+ */
+Array.prototype.findIndex = function findIndex(predicate, thisArg = undefined) {
+  return arrayPrototypeFindHelper(this, predicate, thisArg, false);
+}
+
 var arrayFuncDescriptor = {
   configurable: true,
   enumerable: false,
@@ -485,6 +581,8 @@ Object.defineProperty(Array.prototype, 'every', arrayFuncDescriptor);
 Object.defineProperty(Array.prototype, 'some', arrayFuncDescriptor);
 Object.defineProperty(Array.prototype, 'fill', arrayFuncDescriptor);
 Object.defineProperty(Array.prototype, 'filter', arrayFuncDescriptor);
+Object.defineProperty(Array.prototype, 'find', arrayFuncDescriptor);
+Object.defineProperty(Array.prototype, 'findIndex', arrayFuncDescriptor);
 
 Array.prototype.reverse.prototype = undefined;
 Array.prototype.map.prototype = undefined;
@@ -494,3 +592,5 @@ Array.prototype.every.prototype = undefined;
 Array.prototype.some.prototype = undefined;
 Array.prototype.fill.prototype = undefined;
 Array.prototype.filter.prototype = undefined;
+Array.prototype.find.prototype = undefined;
+Array.prototype.findIndex.prototype = undefined;

lib/VM/JSLib/Array.cpp

@@ -117,21 +117,6 @@ Handle<JSObject> createArrayConstructor(Runtime *runtime) {
       nullptr,
       arrayPrototypeForEach,
       1);
-  defineMethod(
-      runtime,
-      arrayPrototype,
-      Predefined::getSymbolID(Predefined::find),
-      nullptr,
-      arrayPrototypeFind,
-      1);
-  defineMethod(
-      runtime,
-      arrayPrototype,
-      Predefined::getSymbolID(Predefined::findIndex),
-      // Pass a non-null pointer here to indicate we're finding the index.
-      (void *)true,
-      arrayPrototypeFind,
-      1);
   defineMethod(
       runtime,
       arrayPrototype,
@@ -225,6 +210,21 @@ Handle<JSObject> createArrayConstructor(Runtime *runtime) {
       nullptr,
       arrayPrototypeFill,
       1);
+  defineMethod(
+      runtime,
+      arrayPrototype,
+      Predefined::getSymbolID(Predefined::find),
+      nullptr,
+      arrayPrototypeFind,
+      1);
+  defineMethod(
+      runtime,
+      arrayPrototype,
+      Predefined::getSymbolID(Predefined::findIndex),
+      // Pass a non-null pointer here to indicate we're finding the index.
+      (void *)true,
+      arrayPrototypeFind,
+      1);
   defineMethod(
       runtime,
       arrayPrototype,
@@ -2121,72 +2121,6 @@ arrayPrototypeForEach(void *, Runtime *runtime, NativeArgs args) {
   return HermesValue::encodeUndefinedValue();
 }
 
-CallResult<HermesValue>
-arrayPrototypeFind(void *ctx, Runtime *runtime, NativeArgs args) {
-  GCScope gcScope{runtime};
-  bool findIndex = ctx != nullptr;
-  auto objRes = toObject(runtime, args.getThisHandle());
-  if (LLVM_UNLIKELY(objRes == ExecutionStatus::EXCEPTION)) {
-    return ExecutionStatus::EXCEPTION;
-  }
-  auto O = runtime->makeHandle<JSObject>(objRes.getValue());
-
-  // Get the length.
-  auto propRes = JSObject::getNamed_RJS(
-      O, runtime, Predefined::getSymbolID(Predefined::length));
-  if (LLVM_UNLIKELY(propRes == ExecutionStatus::EXCEPTION)) {
-    return ExecutionStatus::EXCEPTION;
-  }
-  auto intRes = toLengthU64(runtime, runtime->makeHandle(*propRes));
-  if (LLVM_UNLIKELY(intRes == ExecutionStatus::EXCEPTION)) {
-    return ExecutionStatus::EXCEPTION;
-  }
-  double len = *intRes;
-
-  auto predicate = args.dyncastArg<Callable>(0);
-  if (!predicate) {
-    return runtime->raiseTypeError("Find argument must be a function");
-  }
-
-  // "this" argument to the callback function.
-  auto T = args.getArgHandle(1);
-
-  MutableHandle<> kHandle{runtime, HermesValue::encodeNumberValue(0)};
-  MutableHandle<> kValue{runtime};
-  auto marker = gcScope.createMarker();
-  while (kHandle->getNumber() < len) {
-    gcScope.flushToMarker(marker);
-    if (LLVM_UNLIKELY(
-            (propRes = JSObject::getComputed_RJS(O, runtime, kHandle)) ==
-            ExecutionStatus::EXCEPTION)) {
-      return ExecutionStatus::EXCEPTION;
-    }
-    kValue = *propRes;
-    auto callRes = Callable::executeCall3(
-        predicate,
-        runtime,
-        T,
-        kValue.getHermesValue(),
-        kHandle.getHermesValue(),
-        O.getHermesValue());
-    if (LLVM_UNLIKELY(callRes == ExecutionStatus::EXCEPTION)) {
-      return ExecutionStatus::EXCEPTION;
-    }
-    bool testResult = toBoolean(*callRes);
-    if (testResult) {
-      // If this is Array.prototype.findIndex, then return the index k.
-      // Else, return the value at the index k.
-      return findIndex ? kHandle.getHermesValue() : kValue.getHermesValue();
-    }
-    kHandle = HermesValue::encodeNumberValue(kHandle->getNumber() + 1);
-  }
-
-  // Failure case for Array.prototype.findIndex is -1.
-  // Failure case for Array.prototype.find is undefined.
-  return findIndex ? HermesValue::encodeNumberValue(-1)
-                   : HermesValue::encodeUndefinedValue();
-}
-
 /// Helper for reduce and reduceRight.
 /// \param reverse set to true to reduceRight, false to reduce from the left.
 static inline CallResult<HermesValue>
@@ -3033,6 +2967,72 @@ arrayPrototypeFilter(void *, Runtime *runtime, NativeArgs args) {
   return A.getHermesValue();
 }
 
+CallResult<HermesValue>
+arrayPrototypeFind(void *ctx, Runtime *runtime, NativeArgs args) {
+  GCScope gcScope{runtime};
+  bool findIndex = ctx != nullptr;
+  auto objRes = toObject(runtime, args.getThisHandle());
+  if (LLVM_UNLIKELY(objRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  auto O = runtime->makeHandle<JSObject>(objRes.getValue());
+
+  // Get the length.
+  auto propRes = JSObject::getNamed_RJS(
+      O, runtime, Predefined::getSymbolID(Predefined::length));
+  if (LLVM_UNLIKELY(propRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  auto intRes = toLengthU64(runtime, runtime->makeHandle(*propRes));
+  if (LLVM_UNLIKELY(intRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  double len = *intRes;
+
+  auto predicate = args.dyncastArg<Callable>(0);
+  if (!predicate) {
+    return runtime->raiseTypeError("Find argument must be a function");
+  }
+
+  // "this" argument to the callback function.
+  auto T = args.getArgHandle(1);
+
+  MutableHandle<> kHandle{runtime, HermesValue::encodeNumberValue(0)};
+  MutableHandle<> kValue{runtime};
+  auto marker = gcScope.createMarker();
+  while (kHandle->getNumber() < len) {
+    gcScope.flushToMarker(marker);
+    if (LLVM_UNLIKELY(
+            (propRes = JSObject::getComputed_RJS(O, runtime, kHandle)) ==
+            ExecutionStatus::EXCEPTION)) {
+      return ExecutionStatus::EXCEPTION;
+    }
+    kValue = *propRes;
+    auto callRes = Callable::executeCall3(
+        predicate,
+        runtime,
+        T,
+        kValue.getHermesValue(),
+        kHandle.getHermesValue(),
+        O.getHermesValue());
+    if (LLVM_UNLIKELY(callRes == ExecutionStatus::EXCEPTION)) {
+      return ExecutionStatus::EXCEPTION;
+    }
+    bool testResult = toBoolean(*callRes);
+    if (testResult) {
+      // If this is Array.prototype.findIndex, then return the index k.
+      // Else, return the value at the index k.
+      return findIndex ? kHandle.getHermesValue() : kValue.getHermesValue();
+    }
+    kHandle = HermesValue::encodeNumberValue(kHandle->getNumber() + 1);
+  }
+
+  // Failure case for Array.prototype.findIndex is -1.
+  // Failure case for Array.prototype.find is undefined.
+  return findIndex ? HermesValue::encodeNumberValue(-1)
+                   : HermesValue::encodeUndefinedValue();
+}
+
 CallResult<HermesValue>
 arrayPrototypeFill(void *, Runtime *runtime, NativeArgs args) {
   GCScope gcScope(runtime);

tools/hvm-bench/arrayFind.js

@@ -0,0 +1,31 @@
+var USE_THISARG = false;
+
+var numIter = 4000;
+var len = 10000;
+var thisArg;
+var a = Array(len);
+for (var i = 0; i < len; i++) {
+  a[i] = i;
+}
+
+if (USE_THISARG) thisArg = a;
+
+function nonFail(val) {
+  return val > 0;
+}
+
+function allFail(val) {
+  return val < 0;
+}
+
+function halfFail(val) {
+  return val >= 5000;
+}
+
+for (var i = 0; i < numIter; i++) {
+  a.find(nonFail, thisArg);
+  a.find(allFail, thisArg);
+  a.find(halfFail, thisArg);
+}
+
+print('done');

tools/hvm-bench/arrayFindIndex.js

@@ -0,0 +1,31 @@
+var USE_THISARG = false;
+
+var numIter = 4000;
+var len = 10000;
+var thisArg;
+var a = Array(len);
+for (var i = 0; i < len; i++) {
+  a[i] = i;
+}
+
+if (USE_THISARG) thisArg = a;
+
+function nonFail(val) {
+  return val > 0;
+}
+
+function allFail(val) {
+  return val < 0;
+}
+
+function halfFail(val) {
+  return val >= 5000;
+}
+
+for (var i = 0; i < numIter; i++) {
+  a.findIndex(nonFail, thisArg);
+  a.findIndex(allFail, thisArg);
+  a.findIndex(halfFail, thisArg);
+}
+
+print('done');