test: replace closure functions with arrow functions

PR-URL: #24522
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/parallel/test-http-write-callbacks.js

@@ -33,7 +33,7 @@ let clientEndCb = false;
let clientIncoming = '';
const clientIncomingExpect = 'asdffoobar';

process.on('exit', function() {
process.on('exit', () => {
  assert(serverEndCb);
  assert.strictEqual(serverIncoming, serverIncomingExpect);
  assert(clientEndCb);
@@ -42,22 +42,22 @@ process.on('exit', function() {
});

// Verify that we get a callback when we do res.write(..., cb)
const server = http.createServer(function(req, res) {
const server = http.createServer((req, res) => {
  res.statusCode = 400;
  res.end('Bad Request.\nMust send Expect:100-continue\n');
});

server.on('checkContinue', function(req, res) {
server.on('checkContinue', (req, res) => {
  server.close();
  assert.strictEqual(req.method, 'PUT');
  res.writeContinue(function() {
  res.writeContinue(() => {
    // continue has been written
    req.on('end', function() {
      res.write('asdf', function(er) {
    req.on('end', () => {
      res.write('asdf', (er) => {
        assert.ifError(er);
        res.write('foo', 'ascii', function(er) {
        res.write('foo', 'ascii', (er) => {
          assert.ifError(er);
          res.end(Buffer.from('bar'), 'buffer', function(er) {
          res.end(Buffer.from('bar'), 'buffer', (er) => {
            serverEndCb = true;
          });
        });
@@ -66,7 +66,7 @@ server.on('checkContinue', function(req, res) {
  });

  req.setEncoding('ascii');
  req.on('data', function(c) {
  req.on('data', (c) => {
    serverIncoming += c;
  });
});
@@ -77,24 +77,24 @@ server.listen(0, function() {
    method: 'PUT',
    headers: { 'expect': '100-continue' }
  });
  req.on('continue', function() {
  req.on('continue', () => {
    // ok, good to go.
    req.write('YmF6', 'base64', function(er) {
    req.write('YmF6', 'base64', (er) => {
      assert.ifError(er);
      req.write(Buffer.from('quux'), function(er) {
      req.write(Buffer.from('quux'), (er) => {
        assert.ifError(er);
        req.end('626c657267', 'hex', function(er) {
        req.end('626c657267', 'hex', (er) => {
          assert.ifError(er);
          clientEndCb = true;
        });
      });
    });
  });
  req.on('response', function(res) {
  req.on('response', (res) => {
    // this should not come until after the end is flushed out
    assert(clientEndCb);
    res.setEncoding('ascii');
    res.on('data', function(c) {
    res.on('data', (c) => {
      clientIncoming += c;
    });
  });