LibJS: Add ArrayPrototype and implement Array.prototype.push()

This function is ultimately supposed to be generic and allow any |this|
that has a length property, but for now it only works on our own Array
object type.

Base/home/anon/js/array.js

@@ -2,6 +2,10 @@ var a = [1, 2, 3];
 
 a[1] = 5;
 
-for (var i = 0; i < 3; ++i) {
+var push_result = a.push(7);
+
+for (var i = 0; i < a.length; ++i) {
     console.log(a[i]);
 }
+
+console.log("push result: " + push_result);

Libraries/LibJS/AST.cpp

@@ -697,7 +697,7 @@ Value ArrayExpression::execute(Interpreter& interpreter) const
 {
     auto* array = interpreter.heap().allocate<Array>();
     for (auto& element : m_elements) {
-        array->append(element.execute(interpreter));
+        array->push(element.execute(interpreter));
     }
     return array;
 }

Libraries/LibJS/Interpreter.cpp

@@ -27,6 +27,7 @@
 #include <AK/Badge.h>
 #include <LibJS/AST.h>
 #include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/ArrayPrototype.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/NativeFunction.h>
 #include <LibJS/Runtime/Object.h>
@@ -42,6 +43,7 @@ Interpreter::Interpreter()
     m_global_object = heap().allocate<GlobalObject>();
     m_object_prototype = heap().allocate<ObjectPrototype>();
     m_string_prototype = heap().allocate<StringPrototype>();
+    m_array_prototype = heap().allocate<ArrayPrototype>();
 }
 
 Interpreter::~Interpreter()
@@ -143,6 +145,7 @@ void Interpreter::gather_roots(Badge<Heap>, HashTable<Cell*>& roots)
     roots.set(m_global_object);
     roots.set(m_string_prototype);
     roots.set(m_object_prototype);
+    roots.set(m_array_prototype);
 
     for (auto& scope : m_scope_stack) {
         for (auto& it : scope.variables) {

Libraries/LibJS/Interpreter.h

@@ -97,6 +97,7 @@ public:
 
     Object* string_prototype() { return m_string_prototype; }
     Object* object_prototype() { return m_object_prototype; }
+    Object* array_prototype() { return m_array_prototype; }
 
 private:
     Heap m_heap;
@@ -107,6 +108,7 @@ private:
     Object* m_global_object { nullptr };
     Object* m_string_prototype { nullptr };
     Object* m_object_prototype { nullptr };
+    Object* m_array_prototype { nullptr };
 };
 
 }

Libraries/LibJS/Makefile

@@ -7,6 +7,7 @@ OBJS = \
     Lexer.o \
     Parser.o \
     Runtime/Array.o \
+    Runtime/ArrayPrototype.o \
     Runtime/Cell.o \
     Runtime/ConsoleObject.o \
     Runtime/Function.o \

Libraries/LibJS/Runtime/Array.cpp

@@ -25,12 +25,14 @@
  */
 
 #include <AK/Function.h>
+#include <LibJS/Interpreter.h>
 #include <LibJS/Runtime/Array.h>
 
 namespace JS {
 
 Array::Array()
 {
+    set_prototype(interpreter().array_prototype());
     put_native_property(
         "length",
         [this](Object*) {
@@ -45,7 +47,7 @@ Array::~Array()
 {
 }
 
-void Array::append(Value value)
+void Array::push(Value value)
 {
     m_elements.append(value);
 }

Libraries/LibJS/Runtime/Array.h

@@ -39,7 +39,7 @@ public:
     const Vector<Value>& elements() const { return m_elements; }
     Vector<Value>& elements() { return m_elements; }
 
-    void append(Value);
+    void push(Value);
 
 private:
     virtual const char* class_name() const override { return "Array"; }

Libraries/LibJS/Runtime/ArrayPrototype.cpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Array.h>
+#include <LibJS/Runtime/ArrayPrototype.h>
+#include <LibJS/Runtime/Value.h>
+
+namespace JS {
+
+ArrayPrototype::ArrayPrototype()
+{
+    put_native_function("push", [](Object* this_object, const Vector<Value>& arguments) -> Value {
+        if (arguments.is_empty())
+            return js_undefined();
+        ASSERT(this_object);
+        ASSERT(this_object->is_array());
+        static_cast<Array*>(this_object)->push(arguments[0]);
+        return Value(static_cast<const Array*>(this_object)->length());
+    });
+}
+
+ArrayPrototype::~ArrayPrototype()
+{
+}
+
+}

Libraries/LibJS/Runtime/ArrayPrototype.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class ArrayPrototype final : public Object {
+public:
+    ArrayPrototype();
+    virtual ~ArrayPrototype() override;
+
+private:
+    virtual const char* class_name() const override { return "ArrayPrototype"; }
+};
+
+}