diff --git a/.eslintrc.json b/.eslintrc.json
index 14d1eb00b4..bfe91b2d11 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -19,17 +19,22 @@
     "@typescript-eslint/no-parameter-properties": ["off"],
     "@typescript-eslint/no-unused-vars": [
       "error",
-      { "argsIgnorePattern": "^_" }
+      { "argsIgnorePattern": "^_", "varsIgnorePattern": "^_" }
     ],
     "@typescript-eslint/ban-ts-ignore": ["off"],
-    "@typescript-eslint/no-empty-function": ["off"],
-    "@typescript-eslint/explicit-function-return-type": ["off"]
+    "@typescript-eslint/no-empty-function": ["off"]
   },
   "overrides": [
     {
-      "files": ["*.ts", "*.tsx"],
+      "files": ["*.js"],
       "rules": {
-        "@typescript-eslint/explicit-function-return-type": ["error"]
+        "@typescript-eslint/explicit-function-return-type": ["off"]
+      }
+    },
+    {
+      "files": ["tools/node_*.js"],
+      "rules": {
+        "@typescript-eslint/no-var-requires": ["off"]
       }
     }
   ]
diff --git a/.prettierignore b/.prettierignore
index 9d83dd750e..695354438c 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1,3 +1,2 @@
-js/flatbuffers.js
 tests/error_syntax.js
 tests/badly_formatted.js
diff --git a/tools/complex_permissions_test.py b/tools/complex_permissions_test.py
index 32385649ba..cc35577ded 100755
--- a/tools/complex_permissions_test.py
+++ b/tools/complex_permissions_test.py
@@ -106,7 +106,7 @@ class TestWritePermissions(BaseReadWritePermissionsTest,
 
 
 class TestNetFetchPermissions(BaseComplexPermissionTest):
-    test_type = "net_fetch"
+    test_type = "netFetch"
 
     def test_allow_localhost_4545(self):
         code, _stdout, stderr = self._run_deno(
@@ -143,7 +143,7 @@ class TestNetFetchPermissions(BaseComplexPermissionTest):
 
 
 class TestNetDialPermissions(BaseComplexPermissionTest):
-    test_type = "net_dial"
+    test_type = "netDial"
 
     def test_allow_localhost_ip_4555(self):
         code, _stdout, stderr = self._run_deno(
@@ -177,7 +177,7 @@ class TestNetDialPermissions(BaseComplexPermissionTest):
 
 
 class TestNetListenPermissions(BaseComplexPermissionTest):
-    test_type = "net_listen"
+    test_type = "netListen"
 
     def test_allow_localhost_4555(self):
         code, _stdout, stderr = self._run_deno(
diff --git a/tools/complex_permissions_test.ts b/tools/complex_permissions_test.ts
index b0e13b6e58..dd65a0e330 100644
--- a/tools/complex_permissions_test.ts
+++ b/tools/complex_permissions_test.ts
@@ -1,28 +1,26 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-const { args, readFileSync, writeFileSync, exit, dial } = Deno;
+const { args, readFileSync, writeFileSync, exit } = Deno;
 
 const name = args[1];
 const test: (args: string[]) => void = {
-  read: (files: string[]): void => {
-    files.forEach((file): any => readFileSync(file));
+  read(files: string[]): void {
+    files.forEach(file => readFileSync(file));
   },
-  write: (files: string[]): void => {
-    files.forEach(
-      (file): any => writeFileSync(file, new Uint8Array(), { append: true })
+  write(files: string[]): void {
+    files.forEach(file =>
+      writeFileSync(file, new Uint8Array(0), { append: true })
     );
   },
-  net_fetch: (hosts: string[]): void => {
-    hosts.forEach((host): any => fetch(host));
+  netFetch(hosts: string[]): void {
+    hosts.forEach(host => fetch(host));
   },
-  net_listen: (hosts: string[]): void => {
-    hosts.forEach(
-      (host): any => {
-        const listener = Deno.listen("tcp", host);
-        listener.close();
-      }
-    );
+  netListen(hosts: string[]): void {
+    hosts.forEach(host => {
+      const listener = Deno.listen("tcp", host);
+      listener.close();
+    });
   },
-  net_dial: async (hosts: string[]): Promise<void> => {
+  async netDial(hosts: string[]): Promise<void> {
     for (const host of hosts) {
       const listener = await Deno.dial("tcp", host);
       listener.close();
diff --git a/tools/deno_http_proxy.ts b/tools/deno_http_proxy.ts
index 0b775ad075..d7a5dda2d0 100644
--- a/tools/deno_http_proxy.ts
+++ b/tools/deno_http_proxy.ts
@@ -15,7 +15,7 @@ async function main(): Promise<void> {
   }
 }
 
-async function proxyRequest(req: ServerRequest) {
+async function proxyRequest(req: ServerRequest): Promise<void> {
   const url = `http://${originAddr}${req.url}`;
   const resp = await fetch(url, {
     method: req.method,
diff --git a/tools/lint.py b/tools/lint.py
index 61c6c59cea..e71d5d0efe 100755
--- a/tools/lint.py
+++ b/tools/lint.py
@@ -38,12 +38,8 @@ def eslint():
     print "eslint"
     script = os.path.join(third_party_path, "node_modules", "eslint", "bin",
                           "eslint")
-    # TODO: Files in 'deno_typescript', 'tools' and 'website' directories are
-    # currently not linted, but they should.
-    source_files = git_ls_files(
-        root_path,
-        ["*.js", "*.ts", ":!:deno_typescript/", ":!:tools/", ":!:website/"])
     # Find all *directories* in the main repo that contain .ts/.js files.
+    source_files = git_ls_files(root_path, ["*.js", "*.ts"])
     source_dirs = set([os.path.dirname(f) for f in source_files])
     # Within the source dirs, eslint does its own globbing, taking into account
     # the exclusion rules listed in '.eslintignore'.
diff --git a/tools/node_tcp_promise.js b/tools/node_tcp_promise.js
index c8fc54aba9..c6de120b1d 100644
--- a/tools/node_tcp_promise.js
+++ b/tools/node_tcp_promise.js
@@ -9,7 +9,7 @@ const response = Buffer.from(
 );
 
 async function write(socket, buffer) {
-  let p = new Promise((resolve, reject) => {
+  const p = new Promise((resolve, _) => {
     socket.write(buffer, resolve);
   });
   return p;
@@ -19,7 +19,7 @@ Server(async socket => {
   socket.on("error", _ => {
     socket.destroy();
   });
-  for await (const data of socket) {
+  for await (const _ of socket) {
     write(socket, response);
   }
 }).listen(port);
diff --git a/tools/permission_prompt_test.ts b/tools/permission_prompt_test.ts
index a4c9e43626..617f8b0fcb 100644
--- a/tools/permission_prompt_test.ts
+++ b/tools/permission_prompt_test.ts
@@ -5,7 +5,7 @@ const firstCheckFailedMessage = "First check failed";
 
 const name = args[1];
 const test = {
-  needsRead: async () => {
+  async needsRead(): Promise<void> {
     try {
       readFileSync("package.json");
     } catch (e) {
@@ -13,7 +13,7 @@ const test = {
     }
     readFileSync("package.json");
   },
-  needsWrite: () => {
+  needsWrite(): void {
     try {
       makeTempDirSync();
     } catch (e) {
@@ -21,7 +21,7 @@ const test = {
     }
     makeTempDirSync();
   },
-  needsEnv: () => {
+  needsEnv(): void {
     try {
       env().home;
     } catch (e) {
@@ -29,7 +29,7 @@ const test = {
     }
     env().home;
   },
-  needsNet: () => {
+  needsNet(): void {
     try {
       listen("tcp", "127.0.0.1:4540");
     } catch (e) {
@@ -37,9 +37,9 @@ const test = {
     }
     listen("tcp", "127.0.0.1:4541");
   },
-  needsRun: () => {
+  needsRun(): void {
     try {
-      const process = run({
+      run({
         args: [
           "python",
           "-c",
@@ -49,7 +49,7 @@ const test = {
     } catch (e) {
       console.log(firstCheckFailedMessage);
     }
-    const process = run({
+    run({
       args: [
         "python",
         "-c",
diff --git a/website/app.ts b/website/app.ts
index c22c0d2c2d..809be51bb4 100644
--- a/website/app.ts
+++ b/website/app.ts
@@ -3,17 +3,71 @@
 // How much to multiply time values in order to process log graphs properly.
 const TimeScaleFactor = 10000;
 
-export async function getJson(path) {
+export interface BenchmarkExecTimeResult {
+  min?: number;
+  max?: number;
+  mean?: number;
+  stddev?: number;
+  system?: number;
+  user?: number;
+}
+
+export interface BenchmarkExecTimeResultSet {
+  [variant: string]: BenchmarkExecTimeResult;
+}
+
+export interface BenchmarkVariantsResultSet {
+  [variant: string]: number;
+}
+
+export interface BenchmarkRun {
+  created_at: string;
+  sha1: string;
+  benchmark: BenchmarkExecTimeResultSet;
+  binary_size?: BenchmarkVariantsResultSet | number;
+  max_memory?: BenchmarkVariantsResultSet | number;
+  bundle_size?: BenchmarkVariantsResultSet;
+  max_latency?: BenchmarkVariantsResultSet;
+  req_per_sec?: BenchmarkVariantsResultSet;
+  req_per_sec_proxy?: BenchmarkVariantsResultSet;
+  syscall_count?: BenchmarkVariantsResultSet;
+  thread_count?: BenchmarkVariantsResultSet;
+  throughput?: BenchmarkVariantsResultSet;
+}
+
+export type BenchmarkName = Exclude<keyof BenchmarkRun, "created_at" | "sha1">;
+
+type Column = [string, ...Array<number | null>];
+
+interface C3DataNode {
+  id: string;
+  index: number;
+  name: string;
+  value: number;
+  x: number;
+}
+
+type C3OnClickCallback = (C3DataNode, unknown) => void;
+type C3OnRenderedCallback = () => void;
+type C3TickFormatter = (number) => number | string;
+
+export async function getJson(path: string): Promise<unknown> {
   return (await fetch(path)).json();
 }
 
-function getBenchmarkVarieties(data, benchmarkName) {
+function getBenchmarkVarieties(
+  data: BenchmarkRun[],
+  benchmarkName: BenchmarkName
+): string[] {
   // Look at last sha hash.
   const last = data[data.length - 1];
   return Object.keys(last[benchmarkName]);
 }
 
-export function createColumns(data, benchmarkName) {
+export function createColumns(
+  data: BenchmarkRun[],
+  benchmarkName: BenchmarkName
+): Column[] {
   const varieties = getBenchmarkVarieties(data, benchmarkName);
   return varieties.map(variety => [
     variety,
@@ -35,11 +89,11 @@ export function createColumns(data, benchmarkName) {
 }
 
 export function createNormalizedColumns(
-  data,
-  benchmarkName,
-  baselineBenchmark,
-  baselineVariety
-) {
+  data: BenchmarkRun[],
+  benchmarkName: BenchmarkName,
+  baselineBenchmark: BenchmarkName,
+  baselineVariety: string
+): Column[] {
   const varieties = getBenchmarkVarieties(data, benchmarkName);
   return varieties.map(variety => [
     variety,
@@ -65,19 +119,19 @@ export function createNormalizedColumns(
   ]);
 }
 
-export function createExecTimeColumns(data) {
+export function createExecTimeColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "benchmark");
 }
 
-export function createThroughputColumns(data) {
+export function createThroughputColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "throughput");
 }
 
-export function createProxyColumns(data) {
+export function createProxyColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "req_per_sec_proxy");
 }
 
-export function createNormalizedProxyColumns(data) {
+export function createNormalizedProxyColumns(data: BenchmarkRun[]): Column[] {
   return createNormalizedColumns(
     data,
     "req_per_sec_proxy",
@@ -86,23 +140,25 @@ export function createNormalizedProxyColumns(data) {
   );
 }
 
-export function createReqPerSecColumns(data) {
+export function createReqPerSecColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "req_per_sec");
 }
 
-export function createNormalizedReqPerSecColumns(data) {
+export function createNormalizedReqPerSecColumns(
+  data: BenchmarkRun[]
+): Column[] {
   return createNormalizedColumns(data, "req_per_sec", "req_per_sec", "hyper");
 }
 
-export function createMaxLatencyColumns(data) {
+export function createMaxLatencyColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "max_latency");
 }
 
-export function createMaxMemoryColumns(data) {
+export function createMaxMemoryColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "max_memory");
 }
 
-export function createBinarySizeColumns(data) {
+export function createBinarySizeColumns(data: BenchmarkRun[]): Column[] {
   const propName = "binary_size";
   const binarySizeNames = Object.keys(data[data.length - 1][propName]);
   return binarySizeNames.map(name => [
@@ -122,7 +178,7 @@ export function createBinarySizeColumns(data) {
   ]);
 }
 
-export function createThreadCountColumns(data) {
+export function createThreadCountColumns(data: BenchmarkRun[]): Column[] {
   const propName = "thread_count";
   const threadCountNames = Object.keys(data[data.length - 1][propName]);
   return threadCountNames.map(name => [
@@ -137,7 +193,7 @@ export function createThreadCountColumns(data) {
   ]);
 }
 
-export function createSyscallCountColumns(data) {
+export function createSyscallCountColumns(data: BenchmarkRun[]): Column[] {
   const propName = "syscall_count";
   const syscallCountNames = Object.keys(data[data.length - 1][propName]);
   return syscallCountNames.map(name => [
@@ -152,27 +208,27 @@ export function createSyscallCountColumns(data) {
   ]);
 }
 
-export function createBundleSizeColumns(data) {
+export function createBundleSizeColumns(data: BenchmarkRun[]): Column[] {
   return createColumns(data, "bundle_size");
 }
 
-export function createSha1List(data) {
+export function createSha1List(data: BenchmarkRun[]): string[] {
   return data.map(d => d.sha1);
 }
 
-export function formatKB(bytes) {
+export function formatKB(bytes: number): string {
   return (bytes / 1024).toFixed(2);
 }
 
-export function formatMB(bytes) {
+export function formatMB(bytes: number): string {
   return (bytes / (1024 * 1024)).toFixed(2);
 }
 
-export function formatReqSec(reqPerSec) {
-  return reqPerSec / 1000;
+export function formatReqSec(reqPerSec: number): string {
+  return (reqPerSec / 1000).toFixed(3);
 }
 
-export function formatPercentage(decimal) {
+export function formatPercentage(decimal: number): string {
   return (decimal * 100).toFixed(2);
 }
 
@@ -186,15 +242,15 @@ export function formatPercentage(decimal) {
  * @param {boolean} zoomEnabled enables the zoom feature
  */
 function generate(
-  id,
-  categories,
-  columns,
-  onclick,
+  id: string,
+  categories: string[],
+  columns: Column[],
+  onclick: C3OnClickCallback,
   yLabel = "",
-  yTickFormat = null,
+  yTickFormat?: C3TickFormatter,
   zoomEnabled = true,
-  onrendered = () => {}
-) {
+  onrendered?: C3OnRenderedCallback
+): void {
   const yAxis = {
     padding: { bottom: 0 },
     min: 0,
@@ -207,12 +263,12 @@ function generate(
     };
     if (yTickFormat == logScale) {
       delete yAxis.min;
-      for (let col of columns) {
+      for (const col of columns) {
         for (let i = 1; i < col.length; i++) {
           if (col[i] == null || col[i] === 0) {
             continue;
           }
-          col[i] = Math.log10(col[i] * TimeScaleFactor);
+          col[i] = Math.log10((col[i] as number) * TimeScaleFactor);
         }
       }
     }
@@ -240,21 +296,14 @@ function generate(
   });
 }
 
-function logScale(t) {
+function logScale(t: number): string {
   return (Math.pow(10, t) / TimeScaleFactor).toFixed(4);
 }
 
-function formatSecsAsMins(t) {
-  // TODO use d3.round()
-  const a = t % 60;
-  const min = Math.floor(t / 60);
-  return a < 30 ? min : min + 1;
-}
-
 /**
  * @param dataUrl The url of benchmark data json.
  */
-export function drawCharts(dataUrl) {
+export function drawCharts(dataUrl: string): Promise<void> {
   // TODO Using window["location"]["hostname"] instead of
   // window.location.hostname because when deno runs app_test.js it gets a type
   // error here, not knowing about window.location.  Ideally Deno would skip
@@ -265,11 +314,8 @@ export function drawCharts(dataUrl) {
   return drawChartsFromBenchmarkData(dataUrl);
 }
 
-const proxyFields = [
-  "req_per_sec"
-  //"max_latency"
-];
-function extractProxyFields(data) {
+const proxyFields: BenchmarkName[] = ["req_per_sec"];
+function extractProxyFields(data: BenchmarkRun[]): void {
   for (const row of data) {
     for (const field of proxyFields) {
       const d = row[field];
@@ -290,8 +336,10 @@ function extractProxyFields(data) {
 /**
  * Draws the charts from the benchmark data stored in gh-pages branch.
  */
-export async function drawChartsFromBenchmarkData(dataUrl) {
-  const data = await getJson(dataUrl);
+export async function drawChartsFromBenchmarkData(
+  dataUrl: string
+): Promise<void> {
+  const data = (await getJson(dataUrl)) as BenchmarkRun[];
 
   // hack to extract proxy fields from req/s fields
   extractProxyFields(data);
@@ -311,25 +359,23 @@ export async function drawChartsFromBenchmarkData(dataUrl) {
   const sha1List = createSha1List(data);
   const sha1ShortList = sha1List.map(sha1 => sha1.substring(0, 6));
 
-  const viewCommitOnClick = _sha1List => d => {
+  function viewCommitOnClick(d: C3DataNode, _: unknown): void {
     // @ts-ignore
-    window.open(
-      `https://github.com/denoland/deno/commit/${_sha1List[d["index"]]}`
-    );
-  };
+    window.open(`https://github.com/denoland/deno/commit/${sha1List[d.index]}`);
+  }
 
   function gen(
-    id,
-    columns,
+    id: string,
+    columns: Column[],
     yLabel = "",
-    yTickFormat = null,
-    onrendered = () => {}
-  ) {
+    yTickFormat?: C3TickFormatter,
+    onrendered?: C3OnRenderedCallback
+  ): void {
     generate(
       id,
       sha1ShortList,
       columns,
-      viewCommitOnClick(sha1List),
+      viewCommitOnClick,
       yLabel,
       yTickFormat,
       true,
@@ -363,8 +409,8 @@ export async function drawChartsFromBenchmarkData(dataUrl) {
   gen("#bundle-size-chart", bundleSizeColumns, "kilobytes", formatKB);
 }
 
-function hideOnRender(elementID) {
-  return () => {
+function hideOnRender(elementID: string): C3OnRenderedCallback {
+  return (): void => {
     const chart = window["document"].getElementById(elementID);
     if (!chart.getAttribute("data-inital-hide-done")) {
       chart.setAttribute("data-inital-hide-done", "true");
@@ -373,12 +419,16 @@ function hideOnRender(elementID) {
   };
 }
 
-function registerNormalizedSwitcher(checkboxID, chartID, normalizedChartID) {
+function registerNormalizedSwitcher(
+  checkboxID: string,
+  chartID: string,
+  normalizedChartID: string
+): void {
   const checkbox = window["document"].getElementById(checkboxID);
   const regularChart = window["document"].getElementById(chartID);
   const normalizedChart = window["document"].getElementById(normalizedChartID);
 
-  checkbox.addEventListener("change", event => {
+  checkbox.addEventListener("change", _ => {
     // If checked is true the normalized variant should be shown
     // @ts-ignore
     if (checkbox.checked) {
@@ -395,15 +445,15 @@ export function main(): void {
   window["chartWidth"] = 800;
   const overlay = window["document"].getElementById("spinner-overlay");
 
-  function showSpinner() {
+  function showSpinner(): void {
     overlay.style.display = "block";
   }
 
-  function hideSpinner() {
+  function hideSpinner(): void {
     overlay.style.display = "none";
   }
 
-  function updateCharts() {
+  function updateCharts(): void {
     const u = window.location.hash.match("all") ? "./data.json" : "recent.json";
 
     showSpinner();
diff --git a/website/app_test.ts b/website/app_test.ts
index c16487585f..cae3a989bf 100644
--- a/website/app_test.ts
+++ b/website/app_test.ts
@@ -1,8 +1,9 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 
-import { test, testPerm, assert, assertEquals } from "../js/test_util.ts";
+import { test, assertEquals } from "../js/test_util.ts";
 import { runIfMain } from "../js/deps/https/deno.land/std/testing/mod.ts";
 import {
+  BenchmarkRun,
   createBinarySizeColumns,
   createExecTimeColumns,
   createThreadCountColumns,
@@ -10,7 +11,8 @@ import {
   createSha1List
 } from "./app.ts";
 
-const regularData = [
+/* eslint-disable @typescript-eslint/camelcase */
+const regularData: BenchmarkRun[] = [
   {
     created_at: "2018-01-01T01:00:00Z",
     sha1: "abcdef",
@@ -97,7 +99,7 @@ const regularData = [
   }
 ];
 
-const irregularData = [
+const irregularData: BenchmarkRun[] = [
   {
     created_at: "2018-01-01T01:00:00Z",
     sha1: "123",
@@ -132,6 +134,7 @@ const irregularData = [
     }
   }
 ];
+/* eslint-enable @typescript-eslint/camelcase */
 
 test(function createExecTimeColumnsRegularData() {
   const columns = createExecTimeColumns(regularData);
diff --git a/website/showdown_toc.js b/website/showdown_toc.js
index ba1f65c719..886036443d 100644
--- a/website/showdown_toc.js
+++ b/website/showdown_toc.js
@@ -25,13 +25,14 @@
   }
 
   function getHeaderEntriesInNodeJs(sourceHtml) {
-    var cheerio = require("cheerio");
-    var $ = cheerio.load(sourceHtml);
-    var headers = $("h1, h2, h3, h4, h5, h6");
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const cheerio = require("cheerio");
+    const $ = cheerio.load(sourceHtml);
+    const headers = $("h1, h2, h3, h4, h5, h6");
 
-    var headerList = [];
-    for (var i = 0; i < headers.length; i++) {
-      var el = headers[i];
+    const headerList = [];
+    for (let i = 0; i < headers.length; i++) {
+      const el = headers[i];
       headerList.push(new TocEntry(el.name, $(el).text(), $(el).attr("id")));
     }
 
@@ -40,14 +41,14 @@
 
   function getHeaderEntriesInBrowser(sourceHtml) {
     // Generate dummy element
-    var source = document.createElement("div");
+    const source = document.createElement("div");
     source.innerHTML = sourceHtml;
 
     // Find headers
-    var headers = source.querySelectorAll("h1, h2, h3, h4, h5, h6");
-    var headerList = [];
-    for (var i = 0; i < headers.length; i++) {
-      var el = headers[i];
+    const headers = source.querySelectorAll("h1, h2, h3, h4, h5, h6");
+    const headerList = [];
+    for (let i = 0; i < headers.length; i++) {
+      const el = headers[i];
       headerList.push(new TocEntry(el.tagName, el.textContent, el.id));
     }
 
@@ -65,8 +66,8 @@
     if (this.children.length === 0) {
       return "";
     }
-    var result = "<ul>\n";
-    for (var i = 0; i < this.children.length; i++) {
+    let result = "<ul>\n";
+    for (let i = 0; i < this.children.length; i++) {
       result += this.children[i].toString();
     }
     result += "</ul>\n";
@@ -74,7 +75,7 @@
   };
 
   TocEntry.prototype.toString = function() {
-    var result = "<li>";
+    let result = "<li>";
     if (this.text) {
       result += '<a href="#' + this.anchor + '">' + this.text + "</a>";
     }
@@ -85,9 +86,8 @@
 
   function sortHeader(tocEntries, level) {
     level = level || 1;
-    var tagName = "H" + level,
-      result = [],
-      currentTocEntry;
+    const tagName = "H" + level;
+    const result = [];
 
     function push(tocEntry) {
       if (tocEntry !== undefined) {
@@ -98,8 +98,9 @@
       }
     }
 
-    for (var i = 0; i < tocEntries.length; i++) {
-      var tocEntry = tocEntries[i];
+    let currentTocEntry;
+    for (let i = 0; i < tocEntries.length; i++) {
+      const tocEntry = tocEntries[i];
       if (tocEntry.tagName.toUpperCase() !== tagName) {
         if (currentTocEntry === undefined) {
           currentTocEntry = new TocEntry();
@@ -118,7 +119,7 @@
   return {
     type: "output",
     filter: function(sourceHtml) {
-      var headerList = getHeaderEntries(sourceHtml);
+      let headerList = getHeaderEntries(sourceHtml);
 
       // No header found
       if (headerList.length === 0) {
@@ -134,7 +135,7 @@
       }
 
       // Build result and replace all [toc]
-      var result =
+      const result =
         '<div class="toc">\n<ul>\n' + headerList.join("") + "</ul>\n</div>\n";
       return sourceHtml.replace(/\[toc\]/gi, result);
     }