diff --git a/jnitrace/src/main.ts b/jnitrace/src/main.ts
index daac360..d052fd1 100644
--- a/jnitrace/src/main.ts
+++ b/jnitrace/src/main.ts
@@ -9,10 +9,10 @@ import { DataTransport } from "./transport/data_transport";
 
 const IS_IN_REPL = true;
 const transport = new DataTransport();
-let config : Config | null = null;
+let config: Config | null = null;
 
 JNILibraryWatcher.setCallback({
-    onLoaded(path : string) {
+    onLoaded(path: string): void {
         if (!IS_IN_REPL && !Config.initialised()) {
             const op = recv("config", (message): void => {
                 const builder = new ConfigBuilder();
@@ -35,7 +35,7 @@ JNILibraryWatcher.setCallback({
             return;
         }
 
-        config.libraries.forEach((element : string) => {
+        config.libraries.forEach((element: string): void => {
             if (path.includes(element)) {
                 send({
                     type: "tracked_library",
@@ -46,17 +46,19 @@ JNILibraryWatcher.setCallback({
     }
 });
 
-const callback : JNIInvocationCallback = {
-    onEnter(args : NativeArgumentValue[]) {
+const callback: JNIInvocationCallback = {
+    onEnter(args: NativeArgumentValue[]): void {
         this.args = args;
     },
-    onLeave(retval : JNINativeReturnValue) {
-        const data = new MethodData(this.methodDef, this.args, retval.get(), this.javaMethod);
+    onLeave(retval: JNINativeReturnValue): void {
+        const data = new MethodData(
+            this.methodDef, this.args, retval.get(), this.javaMethod
+        );
         transport.reportJNIEnvCall(
             data, this.backtrace
         );
     }
-}
+};
 
 JNIInterceptor.attach("DestroyJavaVM", callback);
 JNIInterceptor.attach("AttachCurrentThread", callback);
diff --git a/jnitrace/src/transport/data_transport.ts b/jnitrace/src/transport/data_transport.ts
index 337f19c..a6f5de9 100644
--- a/jnitrace/src/transport/data_transport.ts
+++ b/jnitrace/src/transport/data_transport.ts
@@ -7,6 +7,8 @@ const TYPE_NAME_START = 0;
 const TYPE_NAME_END = -1;
 const SKIP_ENV_INDEX = 1;
 const EMPTY_ARRAY_LEN = 0;
+const JAVA_VM_INDEX = 0;
+const JNI_ENV_INDEX = 0;
 
 
 class NativeMethodJSONContainer {
@@ -137,11 +139,11 @@ class DataTransport {
         this.exclude = [];
     }
 
-    public setIncludeFilter(include: string[]) {
+    public setIncludeFilter(include: string[]): void {
         this.include = include;
     }
 
-    public setExcludeFilter(exclude: string[]) {
+    public setExcludeFilter(exclude: string[]): void {
         this.exclude = exclude;
     }
 
@@ -154,7 +156,7 @@ class DataTransport {
         const outputRet: DataJSONContainer = new DataJSONContainer(
             data.ret, null
         );
-        const javaVM = data.getArgAsPtr(0);
+        const javaVM = data.getArgAsPtr(JAVA_VM_INDEX);
 
         if (!config.vm || this.shouldIgnoreMethod(data)) {
             return;
@@ -180,10 +182,9 @@ class DataTransport {
     ): void {
         const RET_INDEX = 0;
         const config = Config.getInstance();
-        const threadId = Process.getCurrentThreadId();
         const outputArgs: DataJSONContainer[] = [];
         const outputRet: DataJSONContainer[] = [];
-        const jniEnv = data.getArgAsPtr(0);
+        const jniEnv = data.getArgAsPtr(JNI_ENV_INDEX);
 
         this.updateState(data);
 
@@ -338,7 +339,6 @@ class DataTransport {
     }
 
     private shouldIgnoreMethod(data: MethodData): boolean {
-        const config = Config.getInstance();
         const name = data.method.name;
 
         if (this.include.length > EMPTY_ARRAY_LEN) {
@@ -870,7 +870,6 @@ class DataTransport {
         const ENV_ARG_INDEX = 1;
         const VERSION_ARG_INDEX = 2;
 
-        const threadId = Process.getCurrentThreadId();
         const env: NativeArgumentValue = data.args[ENV_ARG_INDEX];
         let binData = null;