diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/openFile.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/openFile.ts
index eabda508..e51a2584 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/openFile.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/openFile.ts
@@ -1,6 +1,6 @@
 import StackFrame from './react-error-overlay/utils/stack-frame';
 
-const isFF = navigator.userAgent.indexOf('Firefox') !== -1;
+const isFF = navigator.userAgent.includes('Firefox');
 
 function openResource(
   fileName: string,
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrame.tsx b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrame.tsx
index 135ce817..993383ab 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrame.tsx
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrame.tsx
@@ -76,7 +76,7 @@ class StackFrame extends Component<Props, State> {
       return null;
     }
     // e.g. "/path-to-my-app/webpack/bootstrap eaddeb46b67d75e4dfc1"
-    const isInternalWebpackBootstrapCode = fileName.trim().indexOf(' ') !== -1;
+    const isInternalWebpackBootstrapCode = fileName.trim().includes(' ');
     if (isInternalWebpackBootstrapCode) {
       return null;
     }
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrameCodeBlock.tsx b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrameCodeBlock.tsx
index 246a137d..aaafdf64 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrameCodeBlock.tsx
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/containers/StackFrameCodeBlock.tsx
@@ -83,7 +83,7 @@ function StackFrameCodeBlock(props: StackFrameCodeBlockPropsType) {
       if (text == null) {
         continue;
       }
-      if (text.indexOf(` ${lineNum} |`) === -1) {
+      if (!text.includes(` ${lineNum} |`)) {
         continue;
       }
       // $FlowFixMe
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getSourceMap.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getSourceMap.ts
index 4b919477..25afb8df 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getSourceMap.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getSourceMap.ts
@@ -88,7 +88,9 @@ export function extractSourceMapUrl(
     match = next;
   }
   if (!(match && match[1])) {
-    return Promise.reject(`Cannot find a source map directive for ${fileUri}.`);
+    return Promise.reject(
+      new Error(`Cannot find a source map directive for ${fileUri}.`),
+    );
   }
   return Promise.resolve(match[1].toString());
 }
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getStackFrames.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getStackFrames.ts
index 04b6ce3b..a49f36c6 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getStackFrames.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/getStackFrames.ts
@@ -51,8 +51,7 @@ function getStackFrames(
     return enhancedFrames.filter(
       ({ functionName, fileName }) =>
         (functionName == null ||
-          functionName.indexOf('__stack_frame_overlay_proxy_console__') ===
-            -1) &&
+          !functionName.includes('__stack_frame_overlay_proxy_console__')) &&
         !toExclude.test(fileName!),
     );
   });
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/isInternalFile.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/isInternalFile.ts
index a0ae7819..de386e5a 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/isInternalFile.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/isInternalFile.ts
@@ -12,9 +12,9 @@ function isInternalFile(
   return (
     sourceFileName == null ||
     sourceFileName === '' ||
-    sourceFileName.indexOf('/~/') !== -1 ||
-    sourceFileName.indexOf('/node_modules/') !== -1 ||
-    sourceFileName.trim().indexOf(' ') !== -1 ||
+    sourceFileName.includes('/~/') ||
+    sourceFileName.includes('/node_modules/') ||
+    sourceFileName.trim().includes(' ') ||
     fileName == null ||
     fileName === ''
   );
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/mapper.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/mapper.ts
index 695ffa33..f285c843 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/mapper.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/mapper.ts
@@ -30,7 +30,7 @@ async function map(
     if (fileName == null) {
       return;
     }
-    if (files.indexOf(fileName) !== -1) {
+    if (files.includes(fileName)) {
       return;
     }
     files.push(fileName);
diff --git a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/parser.ts b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/parser.ts
index 04e4b9ab..f18b7cb4 100644
--- a/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/parser.ts
+++ b/packages/redux-devtools-inspector-monitor-trace-tab/src/react-error-overlay/utils/parser.ts
@@ -50,10 +50,10 @@ function parseStack(stack: string[]): StackFrame[] {
         );
       } else {
         // Strip eval, we don't care about it
-        if (e.indexOf('(eval ') !== -1) {
+        if (e.includes('(eval ')) {
           e = e.replace(/(\(eval at [^()]*)|(\),.*$)/g, '');
         }
-        if (e.indexOf('(at ') !== -1) {
+        if (e.includes('(at ')) {
           e = e.replace(/\(at /, '(');
         }
         const data = e.trim().split(/\s+/g).slice(1);