diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
index a889f3e73e3..099536e068b 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
@@ -33,6 +33,8 @@ import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.types.impl.IrDynamicTypeImpl
 import org.jetbrains.kotlin.ir.util.SymbolTable
 import org.jetbrains.kotlin.ir.util.getPropertyDeclaration
+import org.jetbrains.kotlin.ir.util.kotlinPackageFqn
+import org.jetbrains.kotlin.ir.util.referenceFunction
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
@@ -177,14 +179,14 @@ class JsIrBackendContext(
             override val areEqual
                 get () = TODO("not implemented")
 
-            override val ThrowNullPointerException
-                get () = irBuiltIns.throwNpeSymbol
+            override val ThrowNullPointerException = getFunctions(kotlinPackageFqn.child(Name.identifier("THROW_NPE"))).singleOrNull()?.let {
+                symbolTable.referenceSimpleFunction(it) } ?: irBuiltIns.throwNpeSymbol
 
             override val ThrowNoWhenBranchMatchedException
                 get () = irBuiltIns.noWhenBranchMatchedExceptionSymbol
 
-            override val ThrowTypeCastException
-                get () = irBuiltIns.throwCceSymbol
+            override val ThrowTypeCastException = getFunctions(kotlinPackageFqn.child(Name.identifier("THROW_CCE"))).singleOrNull()?.let {
+                symbolTable.referenceSimpleFunction(it) } ?: irBuiltIns.throwCceSymbol
 
             override val ThrowUninitializedPropertyAccessException=
                 symbolTable.referenceSimpleFunction(getFunctions(FqName("kotlin.throwUninitializedPropertyAccessException")).single())
@@ -205,6 +207,9 @@ class JsIrBackendContext(
         override fun shouldGenerateHandlerParameterForDefaultBodyFun() = true
     }
 
+    val throwISEymbol = getFunctions(kotlinPackageFqn.child(Name.identifier("THROW_CCE"))).singleOrNull()?.let {
+        symbolTable.referenceSimpleFunction(it) } ?: irBuiltIns.throwIseSymbol
+
     val coroutineImplLabelProperty by lazy { ir.symbols.coroutineImpl.getPropertyDeclaration("state")!! }
     val coroutineImplResultSymbol by lazy { ir.symbols.coroutineImpl.getPropertyDeclaration("result")!! }
     val coroutineImplExceptionProperty by lazy { ir.symbols.coroutineImpl.getPropertyDeclaration("exception")!! }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
index d7d08cc7e3b..9ff7e7d60ba 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
@@ -60,6 +60,7 @@ class EnumClassTransformer(val context: JsIrBackendContext, private val irClass:
     private val enumEntries = irClass.declarations.filterIsInstance<IrEnumEntry>()
     private val loweredEnumConstructors = HashMap<IrConstructorSymbol, IrConstructor>()
     private val enumName = irClass.name.identifier
+    private val throwISESymbol = context.throwISEymbol
 
     fun transform(): List<IrDeclaration> {
         // Add `name` and `ordinal` parameters to enum class constructors
@@ -140,7 +141,7 @@ class EnumClassTransformer(val context: JsIrBackendContext, private val irClass:
                             irBranch(
                                 irEquals(irString(it.name.identifier), irGet(nameParameter)), irCall(getInstance)
                             )
-                        } + irElseBranch(irCall(context.irBuiltIns.throwIseSymbol))
+                        } + irElseBranch(irCall(throwISESymbol))
                     )
                 )
             }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/TypeOperatorLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/TypeOperatorLowering.kt
index 5bfa5ea28b4..f767205dc09 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/TypeOperatorLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/TypeOperatorLowering.kt
@@ -42,8 +42,8 @@ class TypeOperatorLowering(val context: JsIrBackendContext) : FileLoweringPass {
     private val calculator = JsIrArithBuilder(context)
 
     //NOTE: Should we define JS-own functions similar to current implementation?
-    private val throwCCE = context.irBuiltIns.throwCceSymbol
-    private val throwNPE = context.irBuiltIns.throwNpeSymbol
+    private val throwCCE = context.ir.symbols.ThrowTypeCastException
+    private val throwNPE = context.ir.symbols.ThrowNullPointerException
 
     private val eqeq = context.irBuiltIns.eqeqSymbol
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrDeclarationToJsTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrDeclarationToJsTransformer.kt
index 6ca24e7b70f..0dd1ff158b8 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrDeclarationToJsTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrDeclarationToJsTransformer.kt
@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.ir.backend.js.transformers.irToJs
 
 import org.jetbrains.kotlin.ir.backend.js.utils.JsGenerationContext
 import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.js.backend.ast.JsDeclarationScope
 import org.jetbrains.kotlin.js.backend.ast.JsEmpty
 import org.jetbrains.kotlin.js.backend.ast.JsStatement
 import org.jetbrains.kotlin.js.backend.ast.JsVars
@@ -23,7 +24,15 @@ class IrDeclarationToJsTransformer : BaseIrElementToJsNodeTransformer<JsStatemen
     }
 
     override fun visitClass(declaration: IrClass, context: JsGenerationContext): JsStatement {
-        return JsClassGenerator(declaration, context).generate()
+        return JsClassGenerator(
+            declaration,
+            context.newDeclaration(
+                JsDeclarationScope(
+                    context.currentScope,
+                    "scope for class ${declaration.name.asString()}"
+                )
+            )
+        ).generate()
     }
 
     override fun visitField(declaration: IrField, context: JsGenerationContext): JsStatement {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/SimpleNameGenerator.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/SimpleNameGenerator.kt
index ff9a7b545ed..265da619d50 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/SimpleNameGenerator.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/SimpleNameGenerator.kt
@@ -181,6 +181,9 @@ class SimpleNameGenerator : NameGenerator {
                         nameBuilder.append(getNameForDeclaration(declaration.parent as IrDeclaration, context))
                         nameBuilder.append('.')
                     }
+                    if (declaration.dispatchReceiverParameter == null) {
+                        nameDeclarator = context.staticContext.rootScope::declareFreshName
+                    }
 
                     nameBuilder.append(declaration.name.asString())
                     // TODO should we skip type parameters and use upper bound of type parameter when print type of value parameters?