<\/span><\/h2>\nNodemon makes it easier to develop.
Under the project’s root dir, do:<\/p>\n
<\/p>\n
npm install --save nodemon\n<\/pre>\n <\/p>\n
Edit package.json file and add the following line:<\/p>\n
\"nodemon\": \"nodemon .\/bin\/www\"\n<\/pre>\nIt becomes like this:<\/p>\n
\"scripts\": {\n \"start\": \"node .\/bin\/www\",\n \"nodemon\": \"nodemon .\/bin\/www\"\n },\n<\/pre>\n <\/p>\n
– Under project’s root dir, create a batch file “run.bat”, then edit it adding the following:<\/p>\n
rem SET DEBUG=node:* & npm start
Note<\/strong>: the commented lines (rem) are alternative commands. <\/p>\n
<\/span>PART4 – INSTALL PostgreSQL\/SEQUELIZE<\/span><\/h2>\nIMPORTANT NOTE:<\/strong><\/p>\nFor the sake of simplicity, it is not required to create a local database for this tutorial.
<\/p>\n
<\/p>\n
Installing potgres:\nnpm install --save sequelize sequelize-cli\nnpm install --save pg pg-hstore\n\nInstalling sequelize:\nnpm install --save sequelize sequelize-cli dotenv\n\nIf necessary:\nnpm audit fix --force\n\nNote: dotenv is used to read envvars.\n<\/pre>\n <\/p>\n
<\/p>\n
<\/span>PART5 – RUNNING THE APP<\/span><\/h2>\nSince this project is a very simple one, everything will be placed in just one file.
Into this file, it is going to be placed the code to run the examples.app.js name<\/em> is merely a convention.If everything is as it was supposed to be, your project’s root dir shall be like this:<\/p>\n
<\/p>\n
The app.js content shall be like this:<\/p>\n
<\/pre>\nvar createError = require('http-errors');\nvar express = require('express');\nvar path = require('path');\nvar cookieParser = require('cookie-parser');\nvar logger = require('morgan');\n\nvar indexRouter = require('.\/routes\/index');\nvar usersRouter = require('.\/routes\/users');\n\nvar app = express();\n\n\/\/ view engine setup\napp.set('views', path.join(__dirname, 'views'));\napp.set('view engine', 'ejs');\n\napp.use(logger('dev'));\napp.use(express.json());\napp.use(express.urlencoded({ extended: false }));\napp.use(cookieParser());\napp.use(express.static(path.join(__dirname, 'public')));\n\napp.use('\/', indexRouter);\napp.use('\/users', usersRouter);\n\n\/\/ catch 404 and forward to error handler\napp.use(function(req, res, next) {\n next(createError(404));\n});\n\n\/\/ error handler\napp.use(function(err, req, res, next) {\n \/\/ set locals, only providing error in development\n res.locals.message = err.message;\n res.locals.error = req.app.get('env') === 'development' ? err : {};\n\n \/\/ render the error page\n res.status(err.status || 500);\n res.render('error');\n});\n\nmodule.exports = app;\n\n<\/pre>\nExecute the “run.bat”.
Point to the site:
If everything is all right, you get this on the browser:<\/p>\n
<\/p>\n
<\/p>\n
Console output:<\/p>\n
<\/p>\n
<\/p>\n
<\/p>\n
<\/p>\n
<\/h2>\n<\/span>PART6 – PLAYING WITH SEQUELIZE<\/span><\/h2>\n<\/span>Testing the Sequelize’s Connection<\/span><\/h3>\nEdit app.js file and place the code below before the “module.exports = app<\/strong>;” statement.<\/p>\nFollow the comments on the snippet below to understand how Sequelize works.
var pg = require('pg');\n\/\/or native libpq bindings\n\/\/var pg = require('pg').native\n\n\/\/ instantiates \nvar Sequelize = require('sequelize')\n , sequelize = new Sequelize({\n username: \"username\",\n password: \"secret\",\n database: \"usename\",\n host: \"xxx.elephantsql.com\",\n port: 5432,\n dialect: \"postgres\"\n});\n\n\/\/ test the connection\nsequelize\n .authenticate()\n .then(function(err) {\n console.log('Connection has been established successfully.');\n }, function (err) { \n console.log('Unable to connect to the database:', err);\n });\n\n<\/pre>\nServer’s output:<\/p>\n
Now that we made sure that the database connection is working fine, stop the application and we may go the next step.<\/p>\n
<\/p>\n
<\/span>Creating Instances<\/span><\/h3>\nWhen the app starts, the sequelize may create your table instances on the database, automatically.
<\/pre>\n\/\/ Define a model to be used by the ORM.\nvar User = sequelize.define('User', {\n username: Sequelize.STRING,\n password: Sequelize.STRING\n}, {\n tableName: 'user', \/\/ this will define the table's name\n \/\/timestamps: false \/\/ this will deactivate the timestamp columns\n})\n\n\n\/\/ PAY ATTENTION TO THIS VARIABLE: if true, sequelize recreates the tables.\nvar recreateDb = true;\n\nsequelize\n .sync({ force: recreateDb }) \/\/ if true, drops and recreates.\n .then(function(err) {\n console.log('It worked!');\n }, function(err) {\n console.log('An error occurred while creating the table:', err);\n });\n\nif (!recreateDb) {\n\n User.create({\n username: 'john-doe',\n password: 'i-am-so-great'\n }).then(function(user) {\n console.log('[INFO]: john-doe persisted');\n \/\/console.log(User)\n })\n\n}\n\n<\/pre>\nStart the application again:
Server’s output:<\/p>\n
<\/p>\n
IMPORTANT<\/strong>:After the instance is created, switch to false the recreateDB var:<\/strong><\/p>\nvar recreateDb = false;<\/p>\n
<\/strong><\/p>\nEach time that you execute the code (or change it) using the configuration where force = true, the table (or tables) is recreated losing its previous content.
sequelize.sync({ force: false })
Check the commented code to take advantage of additional features, uncommenting the chunks to check how it works.<\/p>\n
<\/p>\n
<\/p>\n
<\/h2>\n<\/span>Check To The Datase And Check The Instance Created<\/span><\/h3>\nConnect to the database using a tool.
<\/p>\n
Notice the red arrows. Those fields were created by sequelize.<\/p>\n
<\/p>\n
<\/span>Running Again Using createDB turned to false<\/span><\/h3>\nStop the app (Ctrl+C).<\/p>\n
Go to your code and switch to false the recreateDB var.
<\/p>\n
The server’s output:<\/p>\n
<\/h3>\n<\/h3>\n<\/span>Inserting Data<\/span><\/h3>\nAppend the code below right after the last one and always before the modules.export.<\/p>\n
User.create({\n username: 'John Doe',\n password: 'secret'\n}).then(function (user) {\n console.log('[INFO]: John Doe persisted');\n \/\/console.log(User)\n})\n\n<\/pre>\nThe server’s output:<\/p>\n
<\/p>\n
Go to the database and check if the instance was created.<\/p>\n
<\/p>\n
<\/p>\n
Ok! Success.
<\/span>Find An Instance By Primary Key<\/span><\/h3>\nAgain, stop the service (Ctrl+C).
Append the follwing snippet before the modules.export statement (module.exports = app;).<\/p>\n
User.findByPk(1).then(function (user) {\n console.log('------------------------------------------');\n console.log('>findByPk(1):');\n console.log('n\\[INFO]: ' + user.id + \", \" + user.username + '\\n');\n });\n\n<\/pre>\nI preferred to modify the data to create one more instance (Mary Doe).<\/p>\n
<\/p>\n
<\/p>\n
<\/span>Find by User’s name<\/span><\/h3>\nStop the server and comment the previous code, and append the next (below):<\/p>\n
\/\/ find by username\nconst users = User.findAll({\n where: {\n username: 'John Doe'\n }\n}).then(function (data, err) {\n if(!data) {\n console.log('------------------------------------------');\n console.log('[FAIL]: user instance not found due to: ' + err); \n console.log('------------------------------------------');\n } else {\n console.log('------------------------------------------');\n console.log('[SUCCESS]: instance found: '); \n for (u of data) {\n console.log(u.dataValues);\n console.log('\\n>FULL CONTENT ------------------------------------------');\n console.log(u); \n }\n }\n})\n\nRun the server:<\/pre>\nrun.bat<\/p>\n
<\/p>\n
<\/p>\n
<\/p>\n
<\/h3>\n<\/span>List All Instances<\/span><\/h3>\n\n
Again, stop the service (Ctrl+C).
<\/p>\n
\/\/ find all\nconst list = User.findAll().then(function (data, err) {\n if(!data) {\n console.log('------------------------------------------');\n console.log('[FAIL]: user instance not found due to: ' + err); \n console.log('------------------------------------------');\n } else {\n console.log('------------------------------------------');\n console.log('[SUCCESS]: instance found: '); \n for (u of data) {\n console.log(u.dataValues);\n console.log('\\n>FULL CONTENT ------------------------------------------');\n console.log(u); \n }\n }\n})\n\n<\/pre>\n<\/h2>\n <\/p>\n