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

Author: https://github.com/jack-karamanian
Commit: https://github.com/SerenityOS/serenity/commit/57bd194e5a1
Pull-request: https://github.com/SerenityOS/serenity/pull/1682
Reviewed-by: https://github.com/bgianfo

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:

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);