docs: minor change for 09-emq-broker.md (#13352)

docs-en/20-third-party/09-emq-broker.md

@@ -21,17 +21,17 @@ Depending on the current operating system, users can download the installation p
 ### Take the Docker installation of TDengine as an example
 
 ```bash
-    docker exec -it tdengine bash
-    taos
+docker exec -it tdengine bash
+taos
 ```
 
 ### Create Database and Table
 
 ```sql
-    CREATE DATABASE test;
-    USE test;
+CREATE DATABASE test;
+USE test;
 
-    CREATE TABLE sensor_data (ts timestamp, temperature float, humidity float, volume float, PM10 float, pm25 float, SO2 float, NO2 float, CO float, sensor_id NCHAR(255), area TINYINT, coll_time timestamp);
+CREATE TABLE sensor_data (ts timestamp, temperature float, humidity float, volume float, PM10 float, pm25 float, SO2 float, NO2 float, CO float, sensor_id NCHAR(255), area TINYINT, coll_time timestamp);
 ```
 
 Note: The table schema is based on the blog [(In Chinese) Data Transfer, Storage, Presentation, EMQX + TDengine Build MQTT IoT Data Visualization Platform](https://www.taosdata.com/blog/2020/08/04/1722.html) as an example. Subsequent operations are carried out with this blog scenario too. Please modify it according to your actual application scenario.
@@ -81,84 +81,84 @@ Edit the resource configuration to add the key/value pairing for Authorization.
 ## Compose program to mock data
 
 ```javascript
-    // mock.js
-    const mqtt = require('mqtt')
-    const Mock = require('mockjs')
-    const EMQX_SERVER = 'mqtt://localhost:1883'
-    const CLIENT_NUM = 10
-    const STEP = 5000 // Data interval in ms
-    const AWAIT = 5000 // Sleep time after data be written once to avoid data writing too fast
-    const CLIENT_POOL = []
-    startMock()
-    function sleep(timer = 100) {
-      return new Promise(resolve => {
-        setTimeout(resolve, timer)
-      })
-    }
-    async function startMock() {
-      const now = Date.now()
-      for (let i = 0; i < CLIENT_NUM; i++) {
-        const client = await createClient(`mock_client_${i}`)
-        CLIENT_POOL.push(client)
-      }
-      // last 24h every 5s
-      const last = 24 * 3600 * 1000
-      for (let ts = now - last; ts <= now; ts += STEP) {
-        for (const client of CLIENT_POOL) {
-          const mockData = generateMockData()
-          const data = {
-            ...mockData,
-            id: client.clientId,
-            area: 0,
-            ts,
-          }
-          client.publish('sensor/data', JSON.stringify(data))
-        }
-        const dateStr = new Date(ts).toLocaleTimeString()
-        console.log(`${dateStr} send success.`)
-        await sleep(AWAIT)
+// mock.js
+const mqtt = require('mqtt')
+const Mock = require('mockjs')
+const EMQX_SERVER = 'mqtt://localhost:1883'
+const CLIENT_NUM = 10
+const STEP = 5000 // Data interval in ms
+const AWAIT = 5000 // Sleep time after data be written once to avoid data writing too fast
+const CLIENT_POOL = []
+startMock()
+function sleep(timer = 100) {
+  return new Promise(resolve => {
+    setTimeout(resolve, timer)
+  })
+}
+async function startMock() {
+  const now = Date.now()
+  for (let i = 0; i < CLIENT_NUM; i++) {
+    const client = await createClient(`mock_client_${i}`)
+    CLIENT_POOL.push(client)
+  }
+  // last 24h every 5s
+  const last = 24 * 3600 * 1000
+  for (let ts = now - last; ts <= now; ts += STEP) {
+    for (const client of CLIENT_POOL) {
+      const mockData = generateMockData()
+      const data = {
+        ...mockData,
+        id: client.clientId,
+        area: 0,
+        ts,
       }
-      console.log(`Done, use ${(Date.now() - now) / 1000}s`)
-    }
-    /**
-     * Init a virtual mqtt client
-     * @param {string} clientId ClientID
-     */
-    function createClient(clientId) {
-      return new Promise((resolve, reject) => {
-        const client = mqtt.connect(EMQX_SERVER, {
-          clientId,
-        })
-        client.on('connect', () => {
-          console.log(`client ${clientId} connected`)
-          resolve(client)
-        })
-        client.on('reconnect', () => {
-          console.log('reconnect')
-        })
-        client.on('error', (e) => {
-          console.error(e)
-          reject(e)
-        })
-      })
-    }
-    /**
-    * Generate mock data
-    */
-    function generateMockData() {
-     return {
-       "temperature": parseFloat(Mock.Random.float(22, 100).toFixed(2)),
-       "humidity": parseFloat(Mock.Random.float(12, 86).toFixed(2)),
-       "volume": parseFloat(Mock.Random.float(20, 200).toFixed(2)),
-       "PM10": parseFloat(Mock.Random.float(0, 300).toFixed(2)),
-       "pm25": parseFloat(Mock.Random.float(0, 300).toFixed(2)),
-       "SO2": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
-       "NO2": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
-       "CO": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
-       "area": Mock.Random.integer(0, 20),
-       "ts": 1596157444170,
-     }
+      client.publish('sensor/data', JSON.stringify(data))
     }
+    const dateStr = new Date(ts).toLocaleTimeString()
+    console.log(`${dateStr} send success.`)
+    await sleep(AWAIT)
+  }
+  console.log(`Done, use ${(Date.now() - now) / 1000}s`)
+}
+/**
+ * Init a virtual mqtt client
+ * @param {string} clientId ClientID
+ */
+function createClient(clientId) {
+  return new Promise((resolve, reject) => {
+    const client = mqtt.connect(EMQX_SERVER, {
+      clientId,
+    })
+    client.on('connect', () => {
+      console.log(`client ${clientId} connected`)
+      resolve(client)
+    })
+    client.on('reconnect', () => {
+      console.log('reconnect')
+    })
+    client.on('error', (e) => {
+      console.error(e)
+      reject(e)
+    })
+  })
+}
+/**
+* Generate mock data
+*/
+function generateMockData() {
+ return {
+   "temperature": parseFloat(Mock.Random.float(22, 100).toFixed(2)),
+   "humidity": parseFloat(Mock.Random.float(12, 86).toFixed(2)),
+   "volume": parseFloat(Mock.Random.float(20, 200).toFixed(2)),
+   "PM10": parseFloat(Mock.Random.float(0, 300).toFixed(2)),
+   "pm25": parseFloat(Mock.Random.float(0, 300).toFixed(2)),
+   "SO2": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
+   "NO2": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
+   "CO": parseFloat(Mock.Random.float(0, 50).toFixed(2)),
+   "area": Mock.Random.integer(0, 20),
+   "ts": 1596157444170,
+ }
+}
 ```
 
 Note: `CLIENT_NUM` in the code can be set to a smaller value at the beginning of the test to avoid hardware performance be not capable to handle a more significant number of concurrent clients.