benchmark: use let and const instead of var

Use let and const in domain, es, events, fixtures, fs, http,
http2 and misc.

PR-URL: #31518
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

benchmark/domain/domain-fn-args.js

@@ -15,7 +15,7 @@ function main({ n, args }) {
   bench.start();
 
   bdomain.enter();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     if (myArguments.length >= 2) {
       const args = Array.prototype.slice.call(myArguments, 1);
       fn.apply(this, args);

benchmark/es/defaultparams-bench.js

@@ -22,14 +22,14 @@ function defaultParams(x = 1, y = 2) {
 
 function runOldStyleDefaults(n) {
   bench.start();
-  for (var i = 0; i < n; i++)
+  for (let i = 0; i < n; i++)
     oldStyleDefaults();
   bench.end(n);
 }
 
 function runDefaultParams(n) {
   bench.start();
-  for (var i = 0; i < n; i++)
+  for (let i = 0; i < n; i++)
     defaultParams();
   bench.end(n);
 }

benchmark/es/destructuring-bench.js

@@ -9,9 +9,9 @@ const bench = common.createBenchmark(main, {
 });
 
 function runSwapManual(n) {
-  var x, y, r;
+  let x, y, r;
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     x = 1, y = 2;
     r = x;
     x = y;
@@ -23,9 +23,9 @@ function runSwapManual(n) {
 }
 
 function runSwapDestructured(n) {
-  var x, y;
+  let x, y;
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     x = 1, y = 2;
     [x, y] = [y, x];
     assert.strictEqual(x, 2);

benchmark/es/destructuring-object-bench.js

@@ -8,10 +8,9 @@ const bench = common.createBenchmark(main, {
 });
 
 function runNormal(n) {
-  var i = 0;
   const o = { x: 0, y: 1 };
   bench.start();
-  for (; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     /* eslint-disable no-unused-vars */
     const x = o.x;
     const y = o.y;
@@ -22,10 +21,9 @@ function runNormal(n) {
 }
 
 function runDestructured(n) {
-  var i = 0;
   const o = { x: 0, y: 1 };
   bench.start();
-  for (; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     /* eslint-disable no-unused-vars */
     const { x, y, r = 2 } = o;
     /* eslint-enable no-unused-vars */

benchmark/es/foreach-bench.js

@@ -10,8 +10,8 @@ const bench = common.createBenchmark(main, {
 
 function useFor(n, items, count) {
   bench.start();
-  for (var i = 0; i < n; i++) {
-    for (var j = 0; j < count; j++) {
+  for (let i = 0; i < n; i++) {
+    for (let j = 0; j < count; j++) {
       // eslint-disable-next-line no-unused-vars
       const item = items[j];
     }
@@ -21,7 +21,7 @@ function useFor(n, items, count) {
 
 function useForOf(n, items) {
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     // eslint-disable-next-line no-unused-vars
     for (const item of items) {}
   }
@@ -30,8 +30,8 @@ function useForOf(n, items) {
 
 function useForIn(n, items) {
   bench.start();
-  for (var i = 0; i < n; i++) {
-    for (var j in items) {
+  for (let i = 0; i < n; i++) {
+    for (const j in items) {
       // eslint-disable-next-line no-unused-vars
       const item = items[j];
     }
@@ -41,16 +41,16 @@ function useForIn(n, items) {
 
 function useForEach(n, items) {
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     items.forEach((item) => {});
   }
   bench.end(n);
 }
 
 function main({ n, count, method }) {
   const items = new Array(count);
-  var fn;
-  for (var i = 0; i < count; i++)
+  let fn;
+  for (let i = 0; i < count; i++)
     items[i] = i;
 
   switch (method) {

benchmark/es/map-bench.js

@@ -14,7 +14,7 @@ const bench = common.createBenchmark(main, {
 function runObject(n) {
   const m = {};
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m[`i${i}`] = i;
     m[`s${i}`] = String(i);
     assert.strictEqual(String(m[`i${i}`]), m[`s${i}`]);
@@ -27,7 +27,7 @@ function runObject(n) {
 function runNullProtoObject(n) {
   const m = Object.create(null);
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m[`i${i}`] = i;
     m[`s${i}`] = String(i);
     assert.strictEqual(String(m[`i${i}`]), m[`s${i}`]);
@@ -40,7 +40,7 @@ function runNullProtoObject(n) {
 function runNullProtoLiteralObject(n) {
   const m = { __proto__: null };
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m[`i${i}`] = i;
     m[`s${i}`] = String(i);
     assert.strictEqual(String(m[`i${i}`]), m[`s${i}`]);
@@ -56,7 +56,7 @@ StorageObject.prototype = Object.create(null);
 function runStorageObject(n) {
   const m = new StorageObject();
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m[`i${i}`] = i;
     m[`s${i}`] = String(i);
     assert.strictEqual(String(m[`i${i}`]), m[`s${i}`]);
@@ -79,7 +79,7 @@ function fakeMap() {
 function runFakeMap(n) {
   const m = fakeMap();
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m.set(`i${i}`, i);
     m.set(`s${i}`, String(i));
     assert.strictEqual(String(m.get(`i${i}`)), m.get(`s${i}`));
@@ -92,7 +92,7 @@ function runFakeMap(n) {
 function runMap(n) {
   const m = new Map();
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     m.set(`i${i}`, i);
     m.set(`s${i}`, String(i));
     assert.strictEqual(String(m.get(`i${i}`)), m.get(`s${i}`));

benchmark/es/restparams-bench.js

@@ -11,7 +11,7 @@ const bench = common.createBenchmark(main, {
 function copyArguments() {
   const len = arguments.length;
   const args = new Array(len);
-  for (var i = 0; i < len; i++)
+  for (let i = 0; i < len; i++)
     args[i] = arguments[i];
   assert.strictEqual(args[0], 1);
   assert.strictEqual(args[1], 2);
@@ -34,22 +34,22 @@ function useArguments() {
 }
 
 function runCopyArguments(n) {
-  for (var i = 0; i < n; i++)
+  for (let i = 0; i < n; i++)
     copyArguments(1, 2, 'a', 'b');
 }
 
 function runRestArguments(n) {
-  for (var i = 0; i < n; i++)
+  for (let i = 0; i < n; i++)
     restArguments(1, 2, 'a', 'b');
 }
 
 function runUseArguments(n) {
-  for (var i = 0; i < n; i++)
+  for (let i = 0; i < n; i++)
     useArguments(1, 2, 'a', 'b');
 }
 
 function main({ n, method }) {
-  var fn;
+  let fn;
   switch (method) {
     case '':
       // Empty string falls through to next line as default, mostly for tests.

benchmark/es/spread-assign.js

@@ -16,26 +16,25 @@ function main({ n, context, count, rest, method }) {
     src[`p${n}`] = n;
 
   let obj;  // eslint-disable-line no-unused-vars
-  let i;
 
   switch (method) {
     case '':
       // Empty string falls through to next line as default, mostly for tests.
     case '_extend':
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         obj = util._extend({}, src);
       bench.end(n);
       break;
     case 'assign':
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         obj = Object.assign({}, src);
       bench.end(n);
       break;
     case 'spread':
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         obj = { ...src };
       bench.end(n);
       break;

benchmark/es/spread-bench.js

@@ -25,32 +25,32 @@ function makeTest(count, rest) {
 
 function main({ n, context, count, rest, method }) {
   const ctx = context === 'context' ? {} : null;
-  var fn = makeTest(count, rest);
+  let fn = makeTest(count, rest);
   const args = new Array(count);
-  var i;
-  for (i = 0; i < count; i++)
+
+  for (let i = 0; i < count; i++)
     args[i] = i;
 
   switch (method) {
     case '':
       // Empty string falls through to next line as default, mostly for tests.
     case 'apply':
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         fn.apply(ctx, args);
       bench.end(n);
       break;
     case 'spread':
       if (ctx !== null)
         fn = fn.bind(ctx);
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         fn(...args);
       bench.end(n);
       break;
     case 'call-spread':
       bench.start();
-      for (i = 0; i < n; i++)
+      for (let i = 0; i < n; i++)
         fn.call(ctx, ...args);
       bench.end(n);
       break;

benchmark/events/ee-add-remove.js

@@ -8,17 +8,16 @@ function main({ n }) {
   const ee = new events.EventEmitter();
   const listeners = [];
 
-  var k;
-  for (k = 0; k < 10; k += 1)
+  for (let k = 0; k < 10; k += 1)
     listeners.push(() => {});
 
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (let i = 0; i < n; i += 1) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
-    for (k = listeners.length; --k >= 0; /* empty */) {
+    for (let k = listeners.length; --k >= 0; /* empty */) {
       ee.on(dummy, listeners[k]);
     }
-    for (k = listeners.length; --k >= 0; /* empty */) {
+    for (let k = listeners.length; --k >= 0; /* empty */) {
       ee.removeListener(dummy, listeners[k]);
     }
   }

benchmark/events/ee-emit.js

@@ -11,35 +11,34 @@ const bench = common.createBenchmark(main, {
 function main({ n, argc, listeners }) {
   const ee = new EventEmitter();
 
-  for (var k = 0; k < listeners; k += 1)
+  for (let k = 0; k < listeners; k += 1)
     ee.on('dummy', () => {});
 
-  var i;
   switch (argc) {
     case 2:
       bench.start();
-      for (i = 0; i < n; i += 1) {
+      for (let i = 0; i < n; i += 1) {
         ee.emit('dummy', true, 5);
       }
       bench.end(n);
       break;
     case 4:
       bench.start();
-      for (i = 0; i < n; i += 1) {
+      for (let i = 0; i < n; i += 1) {
         ee.emit('dummy', true, 5, 10, false);
       }
       bench.end(n);
       break;
     case 10:
       bench.start();
-      for (i = 0; i < n; i += 1) {
+      for (let i = 0; i < n; i += 1) {
         ee.emit('dummy', true, 5, 10, false, 5, 'string', true, false, 11, 20);
       }
       bench.end(n);
       break;
     default:
       bench.start();
-      for (i = 0; i < n; i += 1) {
+      for (let i = 0; i < n; i += 1) {
         ee.emit('dummy');
       }
       bench.end(n);

benchmark/events/ee-listener-count-on-prototype.js

@@ -7,13 +7,13 @@ const bench = common.createBenchmark(main, { n: [5e7] });
 function main({ n }) {
   const ee = new EventEmitter();
 
-  for (var k = 0; k < 5; k += 1) {
+  for (let k = 0; k < 5; k += 1) {
     ee.on('dummy0', () => {});
     ee.on('dummy1', () => {});
   }
 
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (let i = 0; i < n; i += 1) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
     ee.listenerCount(dummy);
   }

benchmark/events/ee-listeners-many.js

@@ -8,13 +8,13 @@ function main({ n }) {
   const ee = new EventEmitter();
   ee.setMaxListeners(101);
 
-  for (var k = 0; k < 50; k += 1) {
+  for (let k = 0; k < 50; k += 1) {
     ee.on('dummy0', () => {});
     ee.on('dummy1', () => {});
   }
 
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (let i = 0; i < n; i += 1) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
     ee.listeners(dummy);
   }

benchmark/events/ee-listeners.js

@@ -7,13 +7,13 @@ const bench = common.createBenchmark(main, { n: [5e6] });
 function main({ n }) {
   const ee = new EventEmitter();
 
-  for (var k = 0; k < 5; k += 1) {
+  for (let k = 0; k < 5; k += 1) {
     ee.on('dummy0', () => {});
     ee.on('dummy1', () => {});
   }
 
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (let i = 0; i < n; i += 1) {
     const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
     ee.listeners(dummy);
   }