fs: use arrow functions instead of .bind and self

PR-URL: #17137
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/fs.js

@@ -2026,30 +2026,27 @@ ReadStream.prototype._read = function(n) {
     return this.push(null);
 
   // the actual read.
-  var self = this;
-  fs.read(this.fd, pool, pool.used, toRead, this.pos, onread);
-
-  // move the pool positions, and internal position for reading.
-  if (this.pos !== undefined)
-    this.pos += toRead;
-  pool.used += toRead;
-
-  function onread(er, bytesRead) {
+  fs.read(this.fd, pool, pool.used, toRead, this.pos, (er, bytesRead) => {
     if (er) {
-      if (self.autoClose) {
-        self.destroy();
+      if (this.autoClose) {
+        this.destroy();
       }
-      self.emit('error', er);
+      this.emit('error', er);
     } else {
       var b = null;
       if (bytesRead > 0) {
-        self.bytesRead += bytesRead;
+        this.bytesRead += bytesRead;
         b = thisPool.slice(start, start + bytesRead);
       }
 
-      self.push(b);
+      this.push(b);
     }
-  }
+  });
+
+  // move the pool positions, and internal position for reading.
+  if (this.pos !== undefined)
+    this.pos += toRead;
+  pool.used += toRead;
 };
 
 
@@ -2143,7 +2140,7 @@ fs.FileWriteStream = fs.WriteStream; // support the legacy name
 
 
 WriteStream.prototype.open = function() {
-  fs.open(this.path, this.flags, this.mode, function(er, fd) {
+  fs.open(this.path, this.flags, this.mode, (er, fd) => {
     if (er) {
       if (this.autoClose) {
         this.destroy();
@@ -2154,7 +2151,7 @@ WriteStream.prototype.open = function() {
 
     this.fd = fd;
     this.emit('open', fd);
-  }.bind(this));
+  });
 };
 
 
@@ -2168,15 +2165,14 @@ WriteStream.prototype._write = function(data, encoding, cb) {
     });
   }
 
-  var self = this;
-  fs.write(this.fd, data, 0, data.length, this.pos, function(er, bytes) {
+  fs.write(this.fd, data, 0, data.length, this.pos, (er, bytes) => {
     if (er) {
-      if (self.autoClose) {
-        self.destroy();
+      if (this.autoClose) {
+        this.destroy();
       }
       return cb(er);
     }
-    self.bytesWritten += bytes;
+    this.bytesWritten += bytes;
     cb();
   });