diff --git a/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts b/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts
index 430e9e217..8014e71e9 100644
--- a/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts
+++ b/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts
@@ -63,7 +63,7 @@ export interface XhrMem {
     entries: PerformanceResourceTiming[];
   };
   // callback to remove events from xhr once the span ends
-  callbackToRemoveEvents?: Function;
+  callbackToRemoveEvents?: () => void;
 }
 
 export type PropagateTraceHeaderCorsUrl = string | RegExp;
diff --git a/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts b/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts
index c15e84efd..b4884bb89 100644
--- a/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts
+++ b/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts
@@ -24,6 +24,10 @@ const DIAG_LOGGER = api.diag.createComponentLogger({
     '@opentelemetry/opentelemetry-instrumentation-xml-http-request/utils',
 });
 
+function isDocument(value: unknown): value is Document {
+  return typeof Document !== 'undefined' && value instanceof Document;
+}
+
 /**
  * Helper function to determine payload content length for XHR requests
  * @param body
@@ -32,17 +36,17 @@ const DIAG_LOGGER = api.diag.createComponentLogger({
 export function getXHRBodyLength(
   body: Document | XMLHttpRequestBodyInit
 ): number | undefined {
-  if (typeof Document !== 'undefined' && body instanceof Document) {
+  if (isDocument(body)) {
     return new XMLSerializer().serializeToString(document).length;
   }
+
   // XMLHttpRequestBodyInit expands to the following:
-  if (body instanceof Blob) {
-    return body.size;
+  if (typeof body === 'string') {
+    return getByteLength(body);
   }
 
-  // ArrayBuffer | ArrayBufferView
-  if ((body as any).byteLength !== undefined) {
-    return (body as any).byteLength as number;
+  if (body instanceof Blob) {
+    return body.size;
   }
 
   if (body instanceof FormData) {
@@ -53,8 +57,9 @@ export function getXHRBodyLength(
     return getByteLength(body.toString());
   }
 
-  if (typeof body === 'string') {
-    return getByteLength(body);
+  // ArrayBuffer | ArrayBufferView
+  if (body.byteLength !== undefined) {
+    return body.byteLength;
   }
 
   DIAG_LOGGER.warn('unknown body type');
diff --git a/experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts b/experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts
index 823d6f942..e2f74d48b 100644
--- a/experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts
+++ b/experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts
@@ -66,7 +66,7 @@ const XHR_TIMEOUT = 2000;
 const getData = (
   req: XMLHttpRequest,
   url: string,
-  callbackAfterSend: Function,
+  callbackAfterSend: () => void,
   async?: boolean
 ) => {
   // eslint-disable-next-line no-async-promise-executor
@@ -101,7 +101,7 @@ const postData = (
   req: XMLHttpRequest,
   url: string,
   data: Document | XMLHttpRequestBodyInit,
-  callbackAfterSend: Function,
+  callbackAfterSend: () => void,
   async?: boolean
 ) => {
   // eslint-disable-next-line no-async-promise-executor