diff --git a/benchmark/async_hooks/gc-tracking.js b/benchmark/async_hooks/gc-tracking.js
index a569fb8fa92485..d74b2bac463e28 100644
--- a/benchmark/async_hooks/gc-tracking.js
+++ b/benchmark/async_hooks/gc-tracking.js
@@ -22,22 +22,23 @@ function endAfterGC(n) {
 }
 
 function main({ n, method }) {
+  var i;
   switch (method) {
     case 'trackingEnabled':
       bench.start();
-      for (let i = 0; i < n; i++) {
+      for (i = 0; i < n; i++) {
         new AsyncResource('foobar');
       }
       endAfterGC(n);
       break;
     case 'trackingDisabled':
       bench.start();
-      for (let i = 0; i < n; i++) {
+      for (i = 0; i < n; i++) {
         new AsyncResource('foobar', { requireManualDestroy: true });
       }
       endAfterGC(n);
       break;
     default:
-      throw new Error('Unsupported method');
+      throw new Error(`Unsupported method "${method}"`);
   }
 }
diff --git a/benchmark/dgram/bind-params.js b/benchmark/dgram/bind-params.js
index 5f7999f7a39241..ea1f430eed929b 100644
--- a/benchmark/dgram/bind-params.js
+++ b/benchmark/dgram/bind-params.js
@@ -15,10 +15,11 @@ const noop = () => {};
 function main({ n, port, address }) {
   port = port === 'true' ? 0 : undefined;
   address = address === 'true' ? '0.0.0.0' : undefined;
+  var i;
 
   if (port !== undefined && address !== undefined) {
     bench.start();
-    for (let i = 0; i < n; i++) {
+    for (i = 0; i < n; i++) {
       dgram.createSocket('udp4').bind(port, address)
         .on('error', noop)
         .unref();
@@ -26,7 +27,7 @@ function main({ n, port, address }) {
     bench.end(n);
   } else if (port !== undefined) {
     bench.start();
-    for (let i = 0; i < n; i++) {
+    for (i = 0; i < n; i++) {
       dgram.createSocket('udp4')
         .bind(port)
         .on('error', noop)
@@ -35,7 +36,7 @@ function main({ n, port, address }) {
     bench.end(n);
   } else if (port === undefined && address === undefined) {
     bench.start();
-    for (let i = 0; i < n; i++) {
+    for (i = 0; i < n; i++) {
       dgram.createSocket('udp4')
         .bind()
         .on('error', noop)
diff --git a/benchmark/domain/domain-fn-args.js b/benchmark/domain/domain-fn-args.js
index fe912e34d206e8..c889b35442d046 100644
--- a/benchmark/domain/domain-fn-args.js
+++ b/benchmark/domain/domain-fn-args.js
@@ -28,15 +28,6 @@ function main({ n, args }) {
   bench.end(n);
 }
 
-function fn(a, b, c) {
-  if (!a)
-    a = 1;
-
-  if (!b)
-    b = 2;
-
-  if (!c)
-    c = 3;
-
+function fn(a = 1, b = 2, c = 3) {
   return a + b + c;
 }
diff --git a/benchmark/fs/bench-realpath.js b/benchmark/fs/bench-realpath.js
index 6690d7e87b091f..de03e71b42d585 100644
--- a/benchmark/fs/bench-realpath.js
+++ b/benchmark/fs/bench-realpath.js
@@ -16,10 +16,8 @@ function main({ n, pathType }) {
   bench.start();
   if (pathType === 'relative')
     relativePath(n);
-  else if (pathType === 'resolved')
-    resolvedPath(n);
   else
-    throw new Error(`unknown "pathType": ${pathType}`);
+    resolvedPath(n);
 }
 
 function relativePath(n) {
diff --git a/benchmark/fs/bench-realpathSync.js b/benchmark/fs/bench-realpathSync.js
index 1c751156f73d53..7a01bd18cb72bf 100644
--- a/benchmark/fs/bench-realpathSync.js
+++ b/benchmark/fs/bench-realpathSync.js
@@ -15,24 +15,10 @@ const bench = common.createBenchmark(main, {
 
 
 function main({ n, pathType }) {
+  const path = pathType === 'relative' ? relative_path : resolved_path;
   bench.start();
-  if (pathType === 'relative')
-    relativePath(n);
-  else if (pathType === 'resolved')
-    resolvedPath(n);
-  else
-    throw new Error(`unknown "pathType": ${pathType}`);
-  bench.end(n);
-}
-
-function relativePath(n) {
-  for (var i = 0; i < n; i++) {
-    fs.realpathSync(relative_path);
-  }
-}
-
-function resolvedPath(n) {
   for (var i = 0; i < n; i++) {
-    fs.realpathSync(resolved_path);
+    fs.realpathSync(path);
   }
+  bench.end(n);
 }
diff --git a/benchmark/fs/write-stream-throughput.js b/benchmark/fs/write-stream-throughput.js
index 6fe00cde48cabb..60ad47bc4eabe1 100644
--- a/benchmark/fs/write-stream-throughput.js
+++ b/benchmark/fs/write-stream-throughput.js
@@ -36,7 +36,6 @@ function main({ dur, encodingType, size }) {
   try { fs.unlinkSync(filename); } catch (e) {}
 
   var started = false;
-  var ending = false;
   var ended = false;
 
   var f = fs.createWriteStream(filename);
@@ -52,15 +51,9 @@ function main({ dur, encodingType, size }) {
 
 
   function write() {
-    // don't try to write after we end, even if a 'drain' event comes.
-    // v0.8 streams are so sloppy!
-    if (ending)
-      return;
-
     if (!started) {
       started = true;
       setTimeout(function() {
-        ending = true;
         f.end();
       }, dur * 1000);
       bench.start();
diff --git a/benchmark/misc/freelist.js b/benchmark/misc/freelist.js
index 0530255728ffeb..8c3281cc407363 100644
--- a/benchmark/misc/freelist.js
+++ b/benchmark/misc/freelist.js
@@ -12,7 +12,6 @@ function main({ n }) {
   const FreeList = require('internal/freelist');
   const poolSize = 1000;
   const list = new FreeList('test', poolSize, Object);
-  var i;
   var j;
   const used = [];
 
@@ -23,7 +22,7 @@ function main({ n }) {
 
   bench.start();
 
-  for (i = 0; i < n; i++) {
+  for (var i = 0; i < n; i++) {
     // Return all the items to the pool
     for (j = 0; j < poolSize; j++) {
       list.free(used[j]);
diff --git a/benchmark/misc/function_call/index.js b/benchmark/misc/function_call/index.js
index 91efa573597cc7..28561bc48cd7c3 100644
--- a/benchmark/misc/function_call/index.js
+++ b/benchmark/misc/function_call/index.js
@@ -32,11 +32,9 @@ const bench = common.createBenchmark(main, {
 });
 
 function main({ millions, type }) {
-  const n = millions * 1e6;
-
   const fn = type === 'cxx' ? cxx : js;
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (var i = 0; i < millions * 1e6; i++) {
     fn();
   }
   bench.end(millions);
diff --git a/benchmark/misc/object-property-bench.js b/benchmark/misc/object-property-bench.js
index 37da82d88758fd..ddc6faed7fc8b7 100644
--- a/benchmark/misc/object-property-bench.js
+++ b/benchmark/misc/object-property-bench.js
@@ -78,6 +78,6 @@ function main({ millions, method }) {
       runSymbol(n);
       break;
     default:
-      throw new Error('Unexpected method');
+      throw new Error(`Unexpected method "${method}"`);
   }
 }
diff --git a/benchmark/misc/punycode.js b/benchmark/misc/punycode.js
index 7016fa11712bbc..369adcf17d3973 100644
--- a/benchmark/misc/punycode.js
+++ b/benchmark/misc/punycode.js
@@ -55,9 +55,8 @@ function runPunycode(n, val) {
 }
 
 function runICU(n, val) {
-  var i = 0;
   bench.start();
-  for (; i < n; i++)
+  for (var i = 0; i < n; i++)
     usingICU(val);
   bench.end(n);
 }
@@ -76,6 +75,6 @@ function main({ n, val, method }) {
       }
       // fallthrough
     default:
-      throw new Error('Unexpected method');
+      throw new Error(`Unexpected method "${method}"`);
   }
 }
diff --git a/benchmark/module/module-loader.js b/benchmark/module/module-loader.js
index 25f0ece70169e7..58d4dcf81c9316 100644
--- a/benchmark/module/module-loader.js
+++ b/benchmark/module/module-loader.js
@@ -13,12 +13,10 @@ const bench = common.createBenchmark(main, {
 });
 
 function main({ thousands, fullPath, useCache }) {
-  const n = thousands * 1e3;
-
   tmpdir.refresh();
   try { fs.mkdirSync(benchmarkDirectory); } catch (e) {}
 
-  for (var i = 0; i <= n; i++) {
+  for (var i = 0; i <= thousands * 1e3; i++) {
     fs.mkdirSync(`${benchmarkDirectory}${i}`);
     fs.writeFileSync(
       `${benchmarkDirectory}${i}/package.json`,
@@ -31,37 +29,37 @@ function main({ thousands, fullPath, useCache }) {
   }
 
   if (fullPath === 'true')
-    measureFull(n, useCache === 'true');
+    measureFull(thousands, useCache === 'true');
   else
-    measureDir(n, useCache === 'true');
+    measureDir(thousands, useCache === 'true');
 
   tmpdir.refresh();
 }
 
-function measureFull(n, useCache) {
+function measureFull(thousands, useCache) {
   var i;
   if (useCache) {
-    for (i = 0; i <= n; i++) {
+    for (i = 0; i <= thousands * 1e3; i++) {
       require(`${benchmarkDirectory}${i}/index.js`);
     }
   }
   bench.start();
-  for (i = 0; i <= n; i++) {
+  for (i = 0; i <= thousands * 1e3; i++) {
     require(`${benchmarkDirectory}${i}/index.js`);
   }
-  bench.end(n / 1e3);
+  bench.end(thousands);
 }
 
-function measureDir(n, useCache) {
+function measureDir(thousands, useCache) {
   var i;
   if (useCache) {
-    for (i = 0; i <= n; i++) {
+    for (i = 0; i <= thousands * 1e3; i++) {
       require(`${benchmarkDirectory}${i}`);
     }
   }
   bench.start();
-  for (i = 0; i <= n; i++) {
+  for (i = 0; i <= thousands * 1e3; i++) {
     require(`${benchmarkDirectory}${i}`);
   }
-  bench.end(n / 1e3);
+  bench.end(thousands);
 }
diff --git a/benchmark/tls/convertprotocols.js b/benchmark/tls/convertprotocols.js
index 1ee2672bee7bd7..9f4969344d1bcd 100644
--- a/benchmark/tls/convertprotocols.js
+++ b/benchmark/tls/convertprotocols.js
@@ -8,14 +8,15 @@ const bench = common.createBenchmark(main, {
 });
 
 function main({ n }) {
-  var i = 0;
+  const input = ['ABC', 'XYZ123', 'FOO'];
   var m = {};
   // First call dominates results
   if (n > 1) {
-    tls.convertNPNProtocols(['ABC', 'XYZ123', 'FOO'], m);
+    tls.convertNPNProtocols(input, m);
     m = {};
   }
   bench.start();
-  for (; i < n; i++) tls.convertNPNProtocols(['ABC', 'XYZ123', 'FOO'], m);
+  for (var i = 0; i < n; i++)
+    tls.convertNPNProtocols(input, m);
   bench.end(n);
 }
diff --git a/benchmark/util/format.js b/benchmark/util/format.js
index 5f9c4c3b594497..042b8a93ccfcf2 100644
--- a/benchmark/util/format.js
+++ b/benchmark/util/format.js
@@ -22,9 +22,7 @@ const bench = common.createBenchmark(main, {
 
 function main({ n, type }) {
   // For testing, if supplied with an empty type, default to string.
-  type = type || 'string';
-
-  const [first, second] = inputs[type];
+  const [first, second] = inputs[type || 'string'];
 
   bench.start();
   for (var i = 0; i < n; i++) {
diff --git a/benchmark/util/inspect-array.js b/benchmark/util/inspect-array.js
index 74332d18579865..8b3c54aeb942fe 100644
--- a/benchmark/util/inspect-array.js
+++ b/benchmark/util/inspect-array.js
@@ -18,14 +18,13 @@ function main({ n, len, type }) {
   var arr = Array(len);
   var i, opts;
 
-  // For testing, if supplied with an empty type, default to denseArray.
-  type = type || 'denseArray';
-
   switch (type) {
     case 'denseArray_showHidden':
       opts = { showHidden: true };
       arr = arr.fill('denseArray');
       break;
+      // For testing, if supplied with an empty type, default to denseArray.
+    case '':
     case 'denseArray':
       arr = arr.fill('denseArray');
       break;
diff --git a/benchmark/v8/get-stats.js b/benchmark/v8/get-stats.js
index 6ee742858629c2..84a0655f5db4fa 100644
--- a/benchmark/v8/get-stats.js
+++ b/benchmark/v8/get-stats.js
@@ -12,9 +12,8 @@ const bench = common.createBenchmark(main, {
 });
 
 function main({ method, n }) {
-  var i = 0;
   bench.start();
-  for (; i < n; i++)
+  for (var i = 0; i < n; i++)
     v8[method]();
   bench.end(n);
 }
diff --git a/benchmark/vm/run-in-context.js b/benchmark/vm/run-in-context.js
index da8f56a6e0153b..9b57067a19c9ac 100644
--- a/benchmark/vm/run-in-context.js
+++ b/benchmark/vm/run-in-context.js
@@ -17,12 +17,10 @@ function main({ n, breakOnSigint, withSigintListener }) {
   if (withSigintListener)
     process.on('SIGINT', () => {});
 
-  var i = 0;
-
   const contextifiedSandbox = vm.createContext();
 
   bench.start();
-  for (; i < n; i++)
+  for (var i = 0; i < n; i++)
     vm.runInContext('0', contextifiedSandbox, options);
   bench.end(n);
 }
diff --git a/benchmark/vm/run-in-this-context.js b/benchmark/vm/run-in-this-context.js
index 33fd3a34d81f8f..0754287376d58c 100644
--- a/benchmark/vm/run-in-this-context.js
+++ b/benchmark/vm/run-in-this-context.js
@@ -17,10 +17,8 @@ function main({ n, breakOnSigint, withSigintListener }) {
   if (withSigintListener)
     process.on('SIGINT', () => {});
 
-  var i = 0;
-
   bench.start();
-  for (; i < n; i++)
+  for (var i = 0; i < n; i++)
     vm.runInThisContext('0', options);
   bench.end(n);
 }