Merge pull request #3932 from taosdata/feature/TD-1507

[feature]<TD-1507>: add a nodejs checker for nodejs examples

tests/examples/nodejs/nodejsChecker.js

+const taos = require('td2.0-connector');
+
+
+var host = null;
+var port = 6030;
+for(var i = 2; i < global.process.argv.length; i++){
+	var key = global.process.argv[i].split("=")[0];
+	var value = global.process.argv[i].split("=")[1];
+	
+	if("host" == key){
+		host = value;
+	}
+	if("port" == key){
+		port = value;
+	}
+}
+
+if(host == null){
+	console.log("Usage: node nodejsChecker.js host=<hostname> port=<port>");
+	process.exit(0);
+}
+
+// establish connection
+var conn = taos.connect({host:host, user:"root", password:"taosdata",port:port});
+var cursor = conn.cursor(); 
+// create database
+executeSql("create database if not exists test", 0);
+// use db
+executeSql("use test", 0);
+// drop table
+executeSql("drop table if exists test.weather", 0);
+// create table
+executeSql("create table if not exists test.weather(ts timestamp, temperature float, humidity int)", 0);
+// insert
+executeSql("insert into test.weather (ts, temperature, humidity) values(now, 20.5, 34)", 1);
+// select
+executeQuery("select * from test.weather");
+// close connection
+conn.close();
+
+function executeQuery(sql){
+	var start = new Date().getTime();
+	var promise = cursor.query(sql, true);
+	var end = new Date().getTime();
+	printSql(sql, promise != null,(end - start));
+	promise.then(function(result){
+		result.pretty();
+	});
+}
+
+function executeSql(sql, affectRows){
+	var start = new Date().getTime();
+	var promise = cursor.execute(sql);
+	var end = new Date().getTime();
+	printSql(sql, promise == affectRows, (end - start));
+}
+
+function printSql(sql, succeed, cost){
+	console.log("[ "+(succeed ? "OK" : "ERROR!")+" ] time cost: " + cost + " ms, execute statement ====> " + sql);
+}