LibJS: Handle empty strings and arrays in Value::to_number()

 - An empty string is converted to 0
 - An empty array is converted to 0
 - An array with one item is converted to that item's numeric value
 - An array with more than one item is converted to NaN

2 files changed, 12 insertions, 14 deletions

diff --git a/Libraries/LibJS/Runtime/MathObject.cpp b/Libraries/LibJS/Runtime/MathObject.cpp
index e596165659..8f9de1911f 100644
--- a/Libraries/LibJS/Runtime/MathObject.cpp
+++ b/Libraries/LibJS/Runtime/MathObject.cpp
@@ -27,7 +27,6 @@
 #include <AK/FlyString.h>
 #include <AK/Function.h>
 #include <LibJS/Interpreter.h>
-#include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/MathObject.h>
 
 namespace JS {
@@ -47,18 +46,7 @@ Value MathObject::abs(Interpreter& interpreter)
     if (interpreter.call_frame().arguments.is_empty())
         return js_nan();
 
-    auto argument = interpreter.call_frame().arguments[0];
-
-    if (argument.is_array()) {
-        auto& array = *static_cast<const Array*>(argument.as_object());
-        if (array.length() == 0)
-            return Value(0);
-        if (array.length() > 1)
-            return js_nan();
-        argument = array.elements()[0];
-    }
-
-    auto number = argument.to_number();
+    auto number = interpreter.call_frame().arguments[0].to_number();
     if (number.is_nan())
         return js_nan();
     return Value(number.as_double() >= 0 ? number.as_double() : -number.as_double());
diff --git a/Libraries/LibJS/Runtime/Value.cpp b/Libraries/LibJS/Runtime/Value.cpp
index 240d828696..50fd735b41 100644
--- a/Libraries/LibJS/Runtime/Value.cpp
+++ b/Libraries/LibJS/Runtime/Value.cpp
@@ -28,6 +28,7 @@
 #include <AK/String.h>
 #include <LibJS/Heap/Heap.h>
 #include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/Error.h>
 #include <LibJS/Runtime/Object.h>
 #include <LibJS/Runtime/PrimitiveString.h>
@@ -128,7 +129,16 @@ Value Value::to_number() const
     case Type::Undefined:
         return js_nan();
     case Type::Object:
-        return m_value.as_object->to_primitive(Object::PreferredType::Number).to_number();
+        if (m_value.as_object->is_array()) {
+            auto& array = *static_cast<Array*>(m_value.as_object);
+            if (array.length() == 0)
+                return Value(0);
+            if (array.length() > 1)
+                return js_nan();
+            return array.elements()[0].to_number();
+        } else {
+            return m_value.as_object->to_primitive(Object::PreferredType::Number).to_number();
+        }
     }
 
     ASSERT_NOT_REACHED();