diff --git a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart
index 97b14dba82b..1795a14864a 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart
@@ -813,6 +813,11 @@ defaultNoSuchMethod(obj, Invocation i) {
   throw NoSuchMethodError.withInvocation(obj, i);
 }
 
+// TODO(nshahan) Replace with rti.getRuntimeType() when classes representing
+// native types don't have to "pretend" to be Dart classes. Ex:
+// JSNumber -> int or double
+// JSArray<E> -> List<E>
+// NativeFloat32List -> Float32List
 runtimeType(obj) {
   return obj == null ? Null : JS('', '#[dartx.runtimeType]', obj);
 }
diff --git a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/rtti.dart b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/rtti.dart
index e7f8759ca47..ec392377aec 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/rtti.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/rtti.dart
@@ -110,6 +110,34 @@ RecordType getRecordType(_RecordImpl obj) {
   return type;
 }
 
+/// Returns the interceptor for [obj] as needed by the dart:rti library.
+@notNull
+Object getInterceptorForRti(obj) {
+  var classRef;
+  if (obj == null) {
+    classRef = JS_CLASS_REF(Null);
+  } else {
+    switch (JS<String>('!', 'typeof #', obj)) {
+      case 'number':
+        classRef = JS('', 'Math.floor(#) == # ? # : #', obj, obj,
+            JS_CLASS_REF(JSInt), JS_CLASS_REF(JSNumNotInt));
+        break;
+      case 'function':
+        var signature =
+            JS('', '#[#]', obj, JS_GET_NAME(JsGetName.SIGNATURE_NAME));
+        if (signature != null) classRef = JS_CLASS_REF(Function);
+        break;
+      default:
+        // The interceptors for native JavaScript types like bool, string, etc.
+        // (excluding number and function, see above) are stored as a symbolized
+        // property and can be accessed from the native value itself.
+        classRef = JS('', '#[#]', obj, _extensionType);
+    }
+  }
+  if (classRef == null) throw 'Unknown interceptor for object: ($obj)';
+  return JS<Object>('!', '#.prototype', classRef);
+}
+
 /// Returns the runtime representation of the type of obj.
 ///
 /// The resulting object is used internally for runtime type checking. This is
diff --git a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/runtime.dart b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/runtime.dart
index 9d3b79d41bf..ed957fc4b91 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/runtime.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/runtime.dart
@@ -21,12 +21,15 @@ import 'dart:_foreign_helper'
         spread;
 import 'dart:_interceptors'
     show
-        JSArray,
-        jsNull,
-        JSFunction,
-        NativeError,
         JavaScriptObject,
-        LegacyJavaScriptObject;
+        JSArray,
+        JSInt,
+        jsNull,
+        JSNumNotInt,
+        JSFunction,
+        LegacyJavaScriptObject,
+        NativeError;
+
 import 'dart:_internal' as internal show LateError, Symbol;
 import 'dart:_js_helper'
     show
diff --git a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart
index 5d09d5e1dda..feaf99d66a6 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart
@@ -89,6 +89,9 @@ void nativeNonNullAsserts(bool enable) {
   _nativeNonNullAsserts = enable;
 }
 
+/// A JavaScript Symbol used to store the Rti object on a native array.
+final arrayRti = JS('', r'Symbol("$ti")');
+
 final metadata = JS('', 'Symbol("metadata")');
 
 /// A javascript Symbol used to store a canonical version of T? on T.
diff --git a/sdk/lib/_internal/js_dev_runtime/private/foreign_helper.dart b/sdk/lib/_internal/js_dev_runtime/private/foreign_helper.dart
index e7202a7e601..93158376414 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/foreign_helper.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/foreign_helper.dart
@@ -7,6 +7,7 @@ library dart._foreign_helper;
 import 'dart:_interceptors' show JSArray;
 import 'dart:_js_helper' show notNull;
 import 'dart:_js_shared_embedded_names' show JsBuiltin, JsGetName;
+import 'dart:_runtime' as dart show getInterceptorForRti;
 import 'dart:_rti' show Rti;
 
 /**
@@ -299,18 +300,7 @@ external JS_BUILTIN(String typeDescription, JsBuiltin builtin,
 /// Returns the interceptor for [object].
 ///
 // TODO(nshahan) Replace calls at compile time?
-Object getInterceptor(obj) {
-  var classRef;
-  if (obj == null) {
-    classRef = JS_CLASS_REF(Null);
-  } else if (JS<String>('!', 'typeof #', obj) == 'function') {
-    var signature = JS('', '#[#]', obj, JS_GET_NAME(JsGetName.SIGNATURE_NAME));
-    // Dart functions are always tagged with a signature.
-    if (signature != null) classRef = JS_CLASS_REF(Function);
-  }
-  if (classRef == null) throw 'Unknown interceptor for object: ($obj)';
-  return JS<Object>('!', '#.prototype', classRef);
-}
+Object getInterceptor(obj) => dart.getInterceptorForRti(obj);
 
 /// Returns the Rti object for the type for JavaScript arrays via JS-interop.
 ///
diff --git a/sdk/lib/_internal/js_dev_runtime/private/interceptors.dart b/sdk/lib/_internal/js_dev_runtime/private/interceptors.dart
index 0afc965320d..d8c30ecab9c 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/interceptors.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/interceptors.dart
@@ -7,10 +7,12 @@ library dart._interceptors;
 import 'dart:collection';
 import 'dart:_internal' hide Symbol;
 import 'dart:_js_helper';
-import 'dart:_foreign_helper' show JS, JS_GET_FLAG, JSExportName;
+import 'dart:_foreign_helper'
+    show JS, JS_EMBEDDED_GLOBAL, JS_GET_FLAG, JSExportName;
 import 'dart:math' show Random, ln2;
 import 'dart:_rti' as rti show createRuntimeType, Rti;
 import 'dart:_runtime' as dart;
+import 'dart:_js_shared_embedded_names' show ARRAY_RTI_PROPERTY;
 
 part 'js_array.dart';
 part 'js_number.dart';
@@ -115,6 +117,7 @@ class UnknownJavaScriptObject extends LegacyJavaScriptObject {
   const UnknownJavaScriptObject();
 }
 
+@JsPeerInterface(name: 'Error')
 class NativeError extends Interceptor {
   String dartStack() => JS<String>('!', '#.stack', this);
 }
diff --git a/sdk/lib/_internal/js_dev_runtime/private/js_array.dart b/sdk/lib/_internal/js_dev_runtime/private/js_array.dart
index a0ce3d743c6..3ae15ffe30c 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/js_array.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/js_array.dart
@@ -24,6 +24,9 @@ class JSArray<E> implements List<E>, JSIndexable<E> {
     // TODO(jmesserly): this uses special compiler magic to close over the
     // parameterized ES6 'JSArray' class.
     JS('', '#.__proto__ = JSArray.prototype', list);
+    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
+      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
+          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
@@ -31,6 +34,9 @@ class JSArray<E> implements List<E>, JSIndexable<E> {
   factory JSArray.fixed(list) {
     JS('', '#.__proto__ = JSArray.prototype', list);
     JS('', r'#.fixed$length = Array', list);
+    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
+      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
+          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
@@ -38,6 +44,9 @@ class JSArray<E> implements List<E>, JSIndexable<E> {
     JS('', '#.__proto__ = JSArray.prototype', list);
     JS('', r'#.fixed$length = Array', list);
     JS('', r'#.immutable$list = Array', list);
+    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
+      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
+          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
@@ -597,8 +606,7 @@ class JSArray<E> implements List<E>, JSIndexable<E> {
     return ListMapView<E>(this);
   }
 
-  Type get runtimeType =>
-      dart.wrapType(JS('', '#(#)', dart.getGenericClassStatic<List>(), E));
+  Type get runtimeType => List<E>;
 
   Iterable<E> followedBy(Iterable<E> other) =>
       FollowedByIterable<E>.firstEfficient(this, other);
diff --git a/sdk/lib/_internal/js_dev_runtime/private/js_number.dart b/sdk/lib/_internal/js_dev_runtime/private/js_number.dart
index 28d1744fed7..573f549ddb5 100644
--- a/sdk/lib/_internal/js_dev_runtime/private/js_number.dart
+++ b/sdk/lib/_internal/js_dev_runtime/private/js_number.dart
@@ -16,7 +16,7 @@ class JSNumNotInt extends JSNumber implements double {}
 ///
 /// These are made available as extension methods on `Number` in JS.
 @JsPeerInterface(name: 'Number')
-class JSNumber extends Interceptor implements int, double {
+class JSNumber extends Interceptor implements double {
   const JSNumber();
 
   @notNull
@@ -482,7 +482,7 @@ class JSNumber extends Interceptor implements int, double {
       return BigInt.from(this).modPow(BigInt.from(e), BigInt.from(m)).toInt();
     }
 
-    int b = this;
+    int b = JS<int>('!', '#', this);
     if (b < 0 || b > m) {
       b %= m;
     }
@@ -574,7 +574,7 @@ class JSNumber extends Interceptor implements int, double {
     if (this is! int) throwArgumentErrorValue(this);
     if (m <= 0) throw RangeError.range(m, 1, null, "modulus");
     if (m == 1) return 0;
-    int t = this;
+    int t = JS<int>('!', '#', this);
     if ((t < 0) || (t >= m)) t %= m;
     if (t == 1) return 1;
     if ((t == 0) || (t.isEven && m.isEven)) {
@@ -587,7 +587,7 @@ class JSNumber extends Interceptor implements int, double {
   @notNull
   int gcd(@nullCheck int other) {
     if (this is! int) throwArgumentErrorValue(this);
-    int x = this.abs();
+    int x = JS<int>('!', '#', this).abs();
     int y = other.abs();
     if (x == 0) return y;
     if (y == 0) return x;