diff --git a/pkg/dart2wasm/bin/run_wasm.js b/pkg/dart2wasm/bin/run_wasm.js
index 56d5248a3db..3a842fb3bfb 100644
--- a/pkg/dart2wasm/bin/run_wasm.js
+++ b/pkg/dart2wasm/bin/run_wasm.js
@@ -176,6 +176,9 @@ var dart2wasm = {
     getTimeZoneOffsetInSeconds: function(secondsSinceEpoch) {
         return new Date(secondsSinceEpoch * 1000).getTimezoneOffset() * 60;
     },
+    jsonEncode: function(s) {
+        return stringToDartString(JSON.stringify(stringFromDartString(s)));
+    },
 };
 
 function instantiate(filename, imports) {
diff --git a/sdk/lib/_internal/wasm/lib/core_patch.dart b/sdk/lib/_internal/wasm/lib/core_patch.dart
index 29fe06c61aa..e8756c9b4ea 100644
--- a/sdk/lib/_internal/wasm/lib/core_patch.dart
+++ b/sdk/lib/_internal/wasm/lib/core_patch.dart
@@ -15,6 +15,7 @@ import "dart:_internal"
         EfficientLengthIterable,
         FixedLengthListMixin,
         IterableElementError,
+        jsonEncode,
         ListIterator,
         Lists,
         mix64,
@@ -29,6 +30,8 @@ import "dart:_internal"
         writeIntoOneByteString,
         writeIntoTwoByteString;
 
+import "dart:_internal" as _internal show Symbol;
+
 import "dart:collection"
     show
         HashMap,
@@ -50,3 +53,6 @@ import "dart:typed_data"
 import 'dart:wasm';
 
 typedef _Smi = int; // For compatibility with VM patch files
+
+String _symbolToString(Symbol s) =>
+    _internal.Symbol.getName(s as _internal.Symbol);
diff --git a/sdk/lib/_internal/wasm/lib/errors_patch.dart b/sdk/lib/_internal/wasm/lib/errors_patch.dart
index 991d4821572..f1542bd3ec1 100644
--- a/sdk/lib/_internal/wasm/lib/errors_patch.dart
+++ b/sdk/lib/_internal/wasm/lib/errors_patch.dart
@@ -8,13 +8,12 @@ external Never _throwObjectWithStackTrace(Object error, StackTrace stacktrace);
 class Error {
   @patch
   static String _objectToString(Object object) {
-    return object.toString();
+    return 'Instance of ${object._runtimeType}';
   }
 
   @patch
   static String _stringToSafeString(String string) {
-    // TODO(joshualitt): JSON encode string.
-    return string;
+    return jsonEncode(string);
   }
 
   @patch
@@ -82,6 +81,71 @@ class _TypeError extends _Error implements TypeError {
   }
 }
 
+@patch
+class NoSuchMethodError {
+  final Object? _receiver;
+  final Symbol _memberName;
+  final List? _arguments;
+  final Map<Symbol, dynamic>? _namedArguments;
+  final List? _existingArgumentNames;
+
+  @patch
+  factory NoSuchMethodError.withInvocation(
+          Object? receiver, Invocation invocation) =>
+      NoSuchMethodError(receiver, invocation.memberName,
+          invocation.positionalArguments, invocation.namedArguments);
+
+  @patch
+  NoSuchMethodError(Object? receiver, Symbol memberName,
+      List? positionalArguments, Map<Symbol, dynamic>? namedArguments,
+      [List? existingArgumentNames = null])
+      : _receiver = receiver,
+        _memberName = memberName,
+        _arguments = positionalArguments,
+        _namedArguments = namedArguments,
+        _existingArgumentNames = existingArgumentNames;
+
+  @patch
+  String toString() {
+    StringBuffer sb = StringBuffer('');
+    String comma = '';
+    List? arguments = _arguments;
+    if (arguments != null) {
+      for (var argument in arguments) {
+        sb.write(comma);
+        sb.write(Error.safeToString(argument));
+        comma = ', ';
+      }
+    }
+    Map<Symbol, dynamic>? namedArguments = _namedArguments;
+    if (namedArguments != null) {
+      namedArguments.forEach((Symbol key, var value) {
+        sb.write(comma);
+        sb.write(_symbolToString(key));
+        sb.write(": ");
+        sb.write(Error.safeToString(value));
+        comma = ', ';
+      });
+    }
+    String memberName = _symbolToString(_memberName);
+    String receiverText = Error.safeToString(_receiver);
+    String actualParameters = '$sb';
+    List? existingArgumentNames = _existingArgumentNames;
+    if (existingArgumentNames == null) {
+      return "NoSuchMethodError: method not found: '$memberName'\n"
+          "Receiver: ${receiverText}\n"
+          "Arguments: [$actualParameters]";
+    } else {
+      String formalParameters = existingArgumentNames.join(', ');
+      return "NoSuchMethodError: incorrect number of arguments passed to "
+          "method named '$memberName'\n"
+          "Receiver: ${receiverText}\n"
+          "Tried calling: $memberName($actualParameters)\n"
+          "Found: $memberName($formalParameters)";
+    }
+  }
+}
+
 /// Used by Fasta to report a runtime error when a final field with an
 /// initializer is also initialized in a generative constructor.
 ///
diff --git a/sdk/lib/_internal/wasm/lib/internal_patch.dart b/sdk/lib/_internal/wasm/lib/internal_patch.dart
index b6e9a148cc5..a2fd23917ae 100644
--- a/sdk/lib/_internal/wasm/lib/internal_patch.dart
+++ b/sdk/lib/_internal/wasm/lib/internal_patch.dart
@@ -140,3 +140,6 @@ dynamic _callClosure2(dynamic closure, dynamic arg1, dynamic arg2) {
 // Schedule a callback from JS via setTimeout.
 @pragma("wasm:import", "dart2wasm.scheduleCallback")
 external void scheduleCallback(double millis, dynamic Function() callback);
+
+@pragma("wasm:import", "dart2wasm.jsonEncode")
+external String jsonEncode(String object);