tty: refactor to es6

Backport-PR-URL: #19230
PR-URL: #17615
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/tty.js

@@ -39,7 +39,6 @@ function isatty(fd) {
   return Number.isInteger(fd) && fd >= 0 && isTTY(fd);
 }
 
-
 function ReadStream(fd, options) {
   if (!(this instanceof ReadStream))
     return new ReadStream(fd, options);
@@ -66,7 +65,6 @@ ReadStream.prototype.setRawMode = function(flag) {
   this.isRaw = flag;
 };
 
-
 function WriteStream(fd) {
   if (!(this instanceof WriteStream))
     return new WriteStream(fd);
@@ -86,16 +84,15 @@ function WriteStream(fd) {
   // Ref: https://github.com/nodejs/node/pull/1771#issuecomment-119351671
   this._handle.setBlocking(true);
 
-  var winSize = new Array(2);
-  var err = this._handle.getWindowSize(winSize);
+  const winSize = new Array(2);
+  const err = this._handle.getWindowSize(winSize);
   if (!err) {
     this.columns = winSize[0];
     this.rows = winSize[1];
   }
 }
 inherits(WriteStream, net.Socket);
 
-
 WriteStream.prototype.isTTY = true;
 
 WriteStream.prototype.getColorDepth = function(env = process.env) {
@@ -164,25 +161,23 @@ WriteStream.prototype.getColorDepth = function(env = process.env) {
 };
 
 WriteStream.prototype._refreshSize = function() {
-  var oldCols = this.columns;
-  var oldRows = this.rows;
-  var winSize = new Array(2);
-  var err = this._handle.getWindowSize(winSize);
+  const oldCols = this.columns;
+  const oldRows = this.rows;
+  const winSize = new Array(2);
+  const err = this._handle.getWindowSize(winSize);
   if (err) {
     this.emit('error', errors.errnoException(err, 'getWindowSize'));
     return;
   }
-  var newCols = winSize[0];
-  var newRows = winSize[1];
+  const [newCols, newRows] = winSize;
   if (oldCols !== newCols || oldRows !== newRows) {
     this.columns = newCols;
     this.rows = newRows;
     this.emit('resize');
   }
 };
 
-
-// backwards-compat
+// Backwards-compat
 WriteStream.prototype.cursorTo = function(x, y) {
   readline.cursorTo(this, x, y);
 };
@@ -199,5 +194,4 @@ WriteStream.prototype.getWindowSize = function() {
   return [this.columns, this.rows];
 };
 
-
 module.exports = { isatty, ReadStream, WriteStream };