diff --git a/example/redis_client.js b/example/redis_client.js
index eb2e58e..68219c4 100644
--- a/example/redis_client.js
+++ b/example/redis_client.js
@@ -14,7 +14,7 @@ class Client extends EventEmitter {
     this._resp = new Resp()
       .on('error', (error) => this.emit('error', error))
       .on('data', (data) => {
-        let cb = this._queue.shift()
+        const cb = this._queue.shift()
         if (!cb) return this.emit('error', new Error('Unexpected reply: ' + data))
         if (data instanceof Error) cb[1](data)
         else cb[0](data)
@@ -42,31 +42,31 @@ class Client extends EventEmitter {
 
 // tman example/redis_client.js
 tman('simple redis client', function () {
-  let client = new Client(6379)
+  const client = new Client(6379)
 
   tman.it('info', function * () {
-    let res = yield client.cmd('info')
+    const res = yield client.cmd('info')
     console.log('INFO:', res)
     assert.ok(res.indexOf('redis_version') > 0)
   })
 
   tman.it('set', function * () {
-    let res = yield client.cmd('set', 'resp', 'hello')
+    const res = yield client.cmd('set', 'resp', 'hello')
     console.log('SET:', res)
     assert.strictEqual(res, 'OK')
   })
 
   tman.it('get', function * () {
-    let res = yield client.cmd('get', 'resp')
+    const res = yield client.cmd('get', 'resp')
     console.log('GET:', res)
     assert.strictEqual(res, 'hello')
   })
 
   tman.it('ping', function * () {
     let count = 10000
-    let time = Date.now()
+    const time = Date.now()
     while (count--) {
-      let res = yield client.cmd('ping')
+      const res = yield client.cmd('ping')
       assert.strictEqual(res, 'PONG')
     }
     console.log('PING:', (10000 * 1000 / (Date.now() - time)).toFixed(2), 'ops/sec')
diff --git a/index.js b/index.js
index fbee570..22cc976 100644
--- a/index.js
+++ b/index.js
@@ -42,8 +42,8 @@ class Resp extends EventEmitter {
 
   static encodeBufBulk (buf) {
     if (!Buffer.isBuffer(buf)) throw new TypeError(String(buf) + ' must be Buffer object')
-    let prefix = '$' + buf.length + CRLF
-    let buffer = Buffer.allocUnsafe(prefix.length + buf.length + 2)
+    const prefix = '$' + buf.length + CRLF
+    const buffer = Buffer.allocUnsafe(prefix.length + buf.length + 2)
     buffer.write(prefix)
     buf.copy(buffer, prefix.length)
     buffer.write(CRLF, prefix.length + buf.length)
@@ -52,9 +52,9 @@ class Resp extends EventEmitter {
 
   static encodeArray (arr) {
     if (!Array.isArray(arr)) throw new Error(String(arr) + ' must be Array object')
-    let prefix = '*' + arr.length + CRLF
+    const prefix = '*' + arr.length + CRLF
     let length = prefix.length
-    let bufs = [Buffer.from(prefix)]
+    const bufs = [Buffer.from(prefix)]
 
     for (let buf, i = 0, len = arr.length; i < len; i++) {
       buf = arr[i]
@@ -71,7 +71,7 @@ class Resp extends EventEmitter {
     if (!Array.isArray(arr) || arr.length === 0) {
       throw new Error(String(arr) + ' must be array of value')
     }
-    let bulks = Array(arr.length)
+    const bulks = Array(arr.length)
     for (let i = 0, len = arr.length; i < len; i++) {
       bulks[i] = Buffer.isBuffer(arr[i]) ? Resp.encodeBufBulk(arr[i]) : Resp.encodeBulk(arr[i])
     }
@@ -80,7 +80,7 @@ class Resp extends EventEmitter {
 
   // Decode a RESP buffer to RESP value
   static decode (buf, bufBulk) {
-    let res = parseBuffer(buf, 0, bufBulk)
+    const res = parseBuffer(buf, 0, bufBulk)
     if (!res || res.index < buf.length) throw new Error('Parse "' + buf + '" failed')
     if (res instanceof Error) throw res
     return res.content
@@ -105,8 +105,8 @@ class Resp extends EventEmitter {
 
     if (!this._buf) this._buf = buf
     else {
-      let ret = this._buf.length - this._pos
-      let _buf = Buffer.allocUnsafe(buf.length + ret)
+      const ret = this._buf.length - this._pos
+      const _buf = Buffer.allocUnsafe(buf.length + ret)
 
       this._buf.copy(_buf, 0, this._pos)
       buf.copy(_buf, ret)
@@ -115,7 +115,7 @@ class Resp extends EventEmitter {
     }
 
     while (this._pos < this._buf.length) {
-      let result = parseBuffer(this._buf, this._pos, this._bufBulk)
+      const result = parseBuffer(this._buf, this._pos, this._bufBulk)
       if (result == null) {
         this.emit('drain')
         return true
@@ -153,8 +153,8 @@ class ReadRes {
 }
 
 function readBuffer (buf, i) {
-  let start = i
-  let len = buf.length
+  const start = i
+  const len = buf.length
   while (i < len && !isCRLF(buf, i)) i++
   return i >= len ? null : new ReadRes(buf.utf8Slice(start, i), i + 2)
 }
@@ -190,7 +190,7 @@ function parseBuffer (buf, index, bufBulk) {
       if (result == null) return result
       num = parseInteger(result.content)
       if (num == null || num < -1) return new Error('Parse "$" failed, invalid length')
-      let endIndex = result.index + num
+      const endIndex = result.index + num
 
       if (num === -1) {
         // Null Bulk
@@ -231,7 +231,7 @@ function parseBuffer (buf, index, bufBulk) {
 }
 
 function parseInteger (str) {
-  let num = +str
+  const num = +str
   return (str && Number.isInteger(num)) ? num : null
 }
 
diff --git a/test/index.js b/test/index.js
index 8d64f61..f1f1605 100644
--- a/test/index.js
+++ b/test/index.js
@@ -95,7 +95,7 @@ function test (Resp) {
         assert.strictEqual(Resp.decode(Resp.encodeError(new Error('err'))) instanceof Error, true)
         assert.strictEqual(Resp.decode(Resp.encodeError(new Error('err')), true) instanceof Error, true)
 
-        let err = Resp.decode(Resp.encodeError(new TypeError('err')))
+        const err = Resp.decode(Resp.encodeError(new TypeError('err')))
         assert.strictEqual(err.name, 'TypeError')
         assert.strictEqual(err.code, 'TypeError')
         assert.strictEqual(err.message, 'err')
@@ -126,19 +126,19 @@ function test (Resp) {
         assert.throws(function () { Resp.decode(1) })
         assert.throws(function () { Resp.decode(Buffer.from('123')) })
         assert.throws(function () {
-          let buf = Resp.encodeBulk('123')
+          const buf = Resp.encodeBulk('123')
           buf[buf.length - 1] = 0
           Resp.decode(buf)
         })
         assert.throws(function () {
-          let buf = Buffer.concat([Resp.encodeBulk('123'), Buffer.from('1')])
+          const buf = Buffer.concat([Resp.encodeBulk('123'), Buffer.from('1')])
           Resp.decode(buf)
         })
       })
 
       tman.it('new Resp()', function (done) {
-        let result = []
-        let reply = new Resp()
+        const result = []
+        const reply = new Resp()
 
         reply
           .on('data', function (data) {
@@ -160,7 +160,7 @@ function test (Resp) {
       })
 
       tman.it('new Resp({bufBulk: true})', function (done) {
-        let reply = new Resp({bufBulk: true})
+        const reply = new Resp({bufBulk: true})
 
         reply
           .on('data', function (data) {
@@ -174,8 +174,8 @@ function test (Resp) {
       })
 
       tman.it('new Resp(): Pipelining data', function (done) {
-        let result = []
-        let reply = new Resp()
+        const result = []
+        const reply = new Resp()
 
         reply
           .on('data', function (data) {
@@ -193,7 +193,7 @@ function test (Resp) {
       })
 
       tman.it('new Resp(): with non resp buffer', function (done) {
-        let reply = new Resp()
+        const reply = new Resp()
 
         reply
           .on('error', function (error) {
@@ -206,8 +206,8 @@ function test (Resp) {
       })
 
       tman.it('new Resp(): with error data', function (done) {
-        let result = []
-        let reply = new Resp()
+        const result = []
+        const reply = new Resp()
 
         reply
           .on('data', function (data) {
@@ -231,9 +231,9 @@ function test (Resp) {
       tman.it('new Resp(): chaos', function (done) {
         this.timeout(100000)
 
-        let result = []
-        let reply = new Resp()
-        let buf = Resp.encodeArray([
+        const result = []
+        const reply = new Resp()
+        const buf = Resp.encodeArray([
           Resp.encodeNull(),
           Resp.encodeString('OKOKOKOK'),
           Resp.encodeInteger(123456789),
@@ -263,7 +263,7 @@ function test (Resp) {
           })
 
         let start = 0
-        let length = bufs.length
+        const length = bufs.length
         consumer()
 
         function consumer () {
@@ -279,10 +279,10 @@ function test (Resp) {
       tman.it('new Resp(): bench', function (done) {
         this.timeout(100000)
 
-        let result = []
-        let reply = new Resp()
+        const result = []
+        const reply = new Resp()
 
-        let buf = Resp.encodeArray([
+        const buf = Resp.encodeArray([
           Resp.encodeString('OK'),
           Resp.encodeString('QUEUED'),
           Resp.encodeString('QUEUED'),