eslint: add no-var rule

.eslintrc

@@ -5,6 +5,7 @@ extends: standard
 
 rules:
   eqeqeq: 0
+  no-var: 2
   semi: [2, always]
   space-before-function-paren: [2, never]
   yoda: 0

lib/application.js

@@ -183,7 +183,7 @@ function respond() {
   const res = this.res;
   if (res.headersSent || !this.writable) return;
 
-  var body = this.body;
+  let body = this.body;
   const code = this.status;
 
   // ignore body

lib/request.js

@@ -222,7 +222,7 @@ module.exports = {
 
   get host() {
     const proxy = this.app.proxy;
-    var host = proxy && this.get('X-Forwarded-Host');
+    let host = proxy && this.get('X-Forwarded-Host');
     host = host || this.get('Host');
     if (!host) return '';
     return host.split(/\s*,\s*/)[0];

lib/response.js

@@ -435,7 +435,7 @@ module.exports = {
       else val = String(val);
       this.res.setHeader(field, val);
     } else {
-      for (var key in field) {
+      for (const key in field) {
         this.set(key, field[key]);
       }
     }

test/application/respond.js

@@ -36,14 +36,14 @@ describe('app.respond', function(){
 
   describe('when this.type === null', function(){
     it('should not send Content-Type header', function(done){
-      var app = new Koa();
+      const app = new Koa();
 
       app.use(function *(){
         this.body = '';
         this.type = null;
       });
 
-      var server = app.listen();
+      const server = app.listen();
 
       request(server)
         .get('/')

test/request/href.js

@@ -37,7 +37,7 @@ describe('ctx.href', function(){
         port: address.port
       }, function(res){
         res.statusCode.should.equal(200);
-        var buf = '';
+        let buf = '';
         res.setEncoding('utf8');
         res.on('data', function(s){ buf += s; });
         res.on('end', function(){

test/response/redirect.js

@@ -51,7 +51,7 @@ describe('ctx.redirect(url)', function(){
 
     it('should escape the url', function(){
       const ctx = context();
-      var url = '<script>';
+      let url = '<script>';
       ctx.header.accept = 'text/html';
       ctx.redirect(url);
       url = escape(url);

test/response/type.js

@@ -43,7 +43,7 @@ describe('ctx.type=', function(){
 
   describe('with an unknown extension', function(){
     it('should not set a content-type', function(){
-      var ctx = context();
+      const ctx = context();
       ctx.type = 'asdf';
       assert(!ctx.type);
       assert(!ctx.response.header['content-type']);