benchmark: use let instead of var in dgram

benchmark/dgram/array-vs-concat.js

@@ -18,12 +18,12 @@ const bench = common.createBenchmark(main, {
 
 function main({ dur, len, num, type, chunks }) {
   const chunk = [];
-  for (var i = 0; i < chunks; i++) {
+  for (let i = 0; i < chunks; i++) {
     chunk.push(Buffer.allocUnsafe(Math.round(len / chunks)));
   }
 
   // Server
-  var sent = 0;
+  let sent = 0;
   const socket = dgram.createSocket('udp4');
   const onsend = type === 'concat' ? onsendConcat : onsendMulti;
 
@@ -32,7 +32,7 @@ function main({ dur, len, num, type, chunks }) {
       // The setImmediate() is necessary to have event loop progress on OSes
       // that only perform synchronous I/O on nonblocking UDP sockets.
       setImmediate(() => {
-        for (var i = 0; i < num; i++) {
+        for (let i = 0; i < num; i++) {
           socket.send(Buffer.concat(chunk), PORT, '127.0.0.1', onsend);
         }
       });
@@ -44,7 +44,7 @@ function main({ dur, len, num, type, chunks }) {
       // The setImmediate() is necessary to have event loop progress on OSes
       // that only perform synchronous I/O on nonblocking UDP sockets.
       setImmediate(() => {
-        for (var i = 0; i < num; i++) {
+        for (let i = 0; i < num; i++) {
           socket.send(chunk, PORT, '127.0.0.1', onsend);
         }
       });

benchmark/dgram/bind-params.js

@@ -15,19 +15,18 @@ 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 (i = 0; i < n; i++) {
+    for (let i = 0; i < n; i++) {
       dgram.createSocket('udp4').bind(port, address)
         .on('error', noop)
         .unref();
     }
     bench.end(n);
   } else if (port !== undefined) {
     bench.start();
-    for (i = 0; i < n; i++) {
+    for (let i = 0; i < n; i++) {
       dgram.createSocket('udp4')
         .bind(port)
         .on('error', noop)
@@ -36,7 +35,7 @@ function main({ n, port, address }) {
     bench.end(n);
   } else if (port === undefined && address === undefined) {
     bench.start();
-    for (i = 0; i < n; i++) {
+    for (let i = 0; i < n; i++) {
       dgram.createSocket('udp4')
         .bind()
         .on('error', noop)

benchmark/dgram/multi-buffer.js

@@ -18,19 +18,19 @@ const bench = common.createBenchmark(main, {
 
 function main({ dur, len, num, type, chunks }) {
   const chunk = [];
-  for (var i = 0; i < chunks; i++) {
+  for (let i = 0; i < chunks; i++) {
     chunk.push(Buffer.allocUnsafe(Math.round(len / chunks)));
   }
-  var sent = 0;
-  var received = 0;
+  let sent = 0;
+  let received = 0;
   const socket = dgram.createSocket('udp4');
 
   function onsend() {
     if (sent++ % num === 0) {
       // The setImmediate() is necessary to have event loop progress on OSes
       // that only perform synchronous I/O on nonblocking UDP sockets.
       setImmediate(() => {
-        for (var i = 0; i < num; i++) {
+        for (let i = 0; i < num; i++) {
           socket.send(chunk, PORT, '127.0.0.1', onsend);
         }
       });

benchmark/dgram/offset-length.js

@@ -17,16 +17,16 @@ const bench = common.createBenchmark(main, {
 
 function main({ dur, len, num, type }) {
   const chunk = Buffer.allocUnsafe(len);
-  var sent = 0;
-  var received = 0;
+  let sent = 0;
+  let received = 0;
   const socket = dgram.createSocket('udp4');
 
   function onsend() {
     if (sent++ % num === 0) {
       // The setImmediate() is necessary to have event loop progress on OSes
       // that only perform synchronous I/O on nonblocking UDP sockets.
       setImmediate(() => {
-        for (var i = 0; i < num; i++) {
+        for (let i = 0; i < num; i++) {
           socket.send(chunk, 0, chunk.length, PORT, '127.0.0.1', onsend);
         }
       });

benchmark/dgram/single-buffer.js

@@ -17,16 +17,16 @@ const bench = common.createBenchmark(main, {
 
 function main({ dur, len, num, type }) {
   const chunk = Buffer.allocUnsafe(len);
-  var sent = 0;
-  var received = 0;
+  let sent = 0;
+  let received = 0;
   const socket = dgram.createSocket('udp4');
 
   function onsend() {
     if (sent++ % num === 0) {
       // The setImmediate() is necessary to have event loop progress on OSes
       // that only perform synchronous I/O on nonblocking UDP sockets.
       setImmediate(() => {
-        for (var i = 0; i < num; i++) {
+        for (let i = 0; i < num; i++) {
           socket.send(chunk, PORT, '127.0.0.1', onsend);
         }
       });