test: refactor test-dgram-multicast-set-interface-lo.js

Convert functions to arrow functions. Remove unused param('signal') from
function.

PR-URL: #30536
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/internet/test-dgram-multicast-set-interface-lo.js

@@ -83,8 +83,14 @@ if (process.argv[2] !== 'child') {
   let i = 0;
   let done = 0;
   let timer = null;
+
+  const killSubprocesses = (subprocesses) => {
+    for (const i in subprocesses)
+      subprocesses[i].kill();
+  };
+
   // Exit the test if it doesn't succeed within the TIMEOUT.
-  timer = setTimeout(function() {
+  timer = setTimeout(() => {
     console.error('[PARENT] Responses were not received within %d ms.',
                   TIMEOUT);
     console.error('[PARENT] Skip');
@@ -115,7 +121,7 @@ if (process.argv[2] !== 'child') {
     worker.messagesNeeded = messagesNeeded;
 
     // Handle the death of workers.
-    worker.on('exit', function(code, signal) {
+    worker.on('exit', (code) => {
       // Don't consider this a true death if the worker has finished
       // successfully or if the exit code is 0.
       if (worker.isDone || code === 0) {
@@ -138,7 +144,7 @@ if (process.argv[2] !== 'child') {
       }
     });
 
-    worker.on('message', function(msg) {
+    worker.on('message', (msg) => {
       if (msg.listening) {
         listening += 1;
 
@@ -162,12 +168,12 @@ if (process.argv[2] !== 'child') {
                         'required number of ' +
                         'messages. Will now compare.');
 
-          Object.keys(workers).forEach(function(pid) {
+          Object.keys(workers).forEach((pid) => {
             const worker = workers[pid];
 
             let count = 0;
 
-            worker.messagesReceived.forEach(function(buf) {
+            worker.messagesReceived.forEach((buf) => {
               for (let i = 0; i < worker.messagesNeeded.length; ++i) {
                 if (buf.toString() === worker.messagesNeeded[i]) {
                   count++;
@@ -201,15 +207,15 @@ if (process.argv[2] !== 'child') {
   // Don't bind the address explicitly when sending and start with
   // the OSes default multicast interface selection.
   sendSocket.bind(common.PORT, ANY[FAM]);
-  sendSocket.on('listening', function() {
+  sendSocket.on('listening', () => {
     console.error(`outgoing iface ${interfaceAddress}`);
   });
 
-  sendSocket.on('close', function() {
+  sendSocket.on('close', () => {
     console.error('[PARENT] sendSocket closed');
   });
 
-  sendSocket.sendNext = function() {
+  sendSocket.sendNext = () => {
     const msg = messages[i++];
 
     if (!msg) {
@@ -228,7 +234,7 @@ if (process.argv[2] !== 'child') {
       buf.length,
       PORTS[msg.mcast],
       msg.mcast,
-      function(err) {
+      (err) => {
         assert.ifError(err);
         console.error('[PARENT] sent %s to %s:%s',
                       util.inspect(buf.toString()),
@@ -238,11 +244,6 @@ if (process.argv[2] !== 'child') {
       }
     );
   };
-
-  function killSubprocesses(subprocesses) {
-    for (const i in subprocesses)
-      subprocesses[i].kill();
-  }
 }
 
 if (process.argv[2] === 'child') {
@@ -258,7 +259,7 @@ if (process.argv[2] === 'child') {
     reuseAddr: true
   });
 
-  listenSocket.on('message', function(buf, rinfo) {
+  listenSocket.on('message', (buf, rinfo) => {
     // Examine udp messages only when they were sent by the parent.
     if (!buf.toString().startsWith(SESSION)) return;
 
@@ -280,7 +281,7 @@ if (process.argv[2] === 'child') {
   });
 
 
-  listenSocket.on('listening', function() {
+  listenSocket.on('listening', () => {
     listenSocket.addMembership(MULTICAST, IFACE);
     process.send({ listening: true });
   });