LibJS: Return false for NaN numbers in Value::to_boolean()

2 files changed, 6 insertions, 0 deletions

diff --git a/Libraries/LibJS/Runtime/Value.cpp b/Libraries/LibJS/Runtime/Value.cpp
index 77d2fcc4f9..6e5d11c3ba 100644
--- a/Libraries/LibJS/Runtime/Value.cpp
+++ b/Libraries/LibJS/Runtime/Value.cpp
@@ -83,6 +83,9 @@ bool Value::to_boolean() const
     case Type::Boolean:
         return m_value.as_bool;
     case Type::Number:
+        if (is_nan()) {
+            return false;
+        }
         return !(m_value.as_double == 0 || m_value.as_double == -0);
     case Type::Null:
     case Type::Undefined:
diff --git a/Libraries/LibJS/Tests/NaN-basic.js b/Libraries/LibJS/Tests/NaN-basic.js
index b9a02bc425..17b51711d6 100644
--- a/Libraries/LibJS/Tests/NaN-basic.js
+++ b/Libraries/LibJS/Tests/NaN-basic.js
@@ -10,6 +10,9 @@ try {
     assert(isNaN(undefined) === true);
     assert(isNaN(null) === false);
     assert(isNaN(Infinity) === false);
+    assert(!!NaN === false);
+    assert(!!nan === false);
+  
     console.log("PASS");
 } catch (e) {
     console.log("FAIL: " + e);