Express-util-tools NPM

Express-Util-Tools

by: rlothbrock.10@gmail.com

This package is intended to provide some common use functions on Express applications, with zero or almost zero dependencies.

Usually, when we are building express applications, we tend to code a lot of boilerplate, over and over again. With this package you will only require the features and pass proper data to make it work.

Usage

Install the package as a dependency on your project npm i express-util-tools

The Catch Async functionalities

When we are building express routes, we build async controllers that may throw Errors. Hence, we need to wrap the logic on try{}catch(e){} blocks to avoid issues. This makes our code a bit noisy if we don't implement some wrapping for those controllers.

The catchAsync and catchWithCustomError functionalities provide such wrappers. The first one uses a built in error class, Meanwhile, the second one allows you to use your own custom error class,

on your controller's file in express routes

const tools = require('express-util-tools');

const MyErrorClass = require('./path');
const putResourceBuilder = require('./path');
const {catchAsync} = tools; 
const customCatch = tools.catchWithCustomError(MyErrorClass);

const getResourceController = async(req, res, next){
    //...some async code that may throw an error
}

const postResourceController = async(req, res, next){
    //...some async code that may throw an error
}


// you can use the wrapper in any of these ways.
module.exports.getResource = catchAsync(getResourceController)
module.exports.postResource = customCatch(postResourceController)
module.exports.patchResource = catchAsync(async(req, res, next)=>{/*...code here...*/})
module.exports.putResource = catchAsync(putResourceBuilder(...args))

The AppError constructor

Even if you can define your own Error instances, this module provides a simple Error constructor to avoid the developer to reinvent the wheel.

With this constructor you can easily define your operational errors and debug them during development phase

const { AppError } = require('express-util-tools');

const getSomeResource = async(req, res, next)=>{

    const { resourceId } = req.body;

    // you can easy declare different error types
    if !resourceId return next( new AppError(400,'request malformed'))

    const resource = await Model.findById(req.body.resourceId);

    // Setting a message its optional. The class has a default message for each type.
    if !resource return next(new AppError(404))


}

The Envelop Functionalities

Usually we need to serialize the router response, and this feature allows us to do it easily.

const tools = require('express-util-tools');

const { envelop} = tools;

postSomeResource = async (req, res, next)=>{

    //...logic here to create the resource
    const resource = {foo:'bar'} // some resource

    return envelop(res, 201, {data: resource});

}

//we can optionally define a custom message

getSomeResource = async (req, res, next)=>{

    //...logic here to get the resource
    const resource = {foo:'bar'} // some resource

    const message = 'Resource successfully sent';

    return envelop(res, 201, {data: resource}, message );

}

The Top Level Error

When we use express, we tend to use middleware a lot. Error handling is not the exception, so we need to declare a global error handler middleware in order to catch all operational errors and redirect them to the request-response flow. That's why this feature was created, to allow the developer handle the error in a simple way.

const tools = require('express-util-tools');
//rest of imports


//at the end of the middleware chain
app.use(tools.topLevel)

The Email feature

This feature allows you to implement the basics of nodemailer in your application with a few lines of code, and without require the package itself.

This feature uses nodemailer 6.7.7

However, this feature doesn't replace nodemailer , so if you are thinking on using nodemailer and its features in depth, you may find this feature insufficient.

Please feel free to make suggestions to improve the feature and make it more useful for complex implementations

Usage of mailer

const {mailer} = require('express-util-tools');

// You can define a plain text version of your email.
const plainTextMessage = `${yourPlainTextMessage}`; 


//Also you can define an html version of your email.
//In order to do this, you need:

// An html template to be parsed. 
const htmlTemplateLocation = path.join(__dirname, "email.template.html");
// data to be injected to the provided template
const yourDataAsArray = [...data];
//optional stylesheet for your template.
const optionalStylesheet = path.join(__dirname, "email.template.css")


//Once you have all this, you can build (asynchronously an html template to be sent )
const htmlMessage = await mailer.buildHTML(
    htmlTemplateLocation, yourDataAsArray,
    { styles: optionalStylesheet });

//The next step is configure the options to be passed to the nodemailer transporter. 
//This method accepts an array as argument and cover the following options:
const mailOptions = mailer.basicEmailOptions(
/*from*/    MAIL_SOURCE_ADDRESS,
/*to*/      recipientAddress,
/*subject*/ subject,
/*text*/    plainTextMessage,
/*html*/    htmlMessage
);
//!Make sure to pass the options in the correct order. 


//Then you either can test your email feature or se it for sending actual emails.
if (process.env.NODE_ENV !== 'production'){

    const devSender =   new mailer.test(); 
    devSender.test(mailOptions).then((mail) => console.log(mailer.getTestMessageUrl(mail)));
}else{

    // you can create transport options for SendGrid. 
    const transporterOptions = mailer.sendGridTransportOptions(
        process.env.SEND_GRID_USER, // this first parameter is optional 
        process.env.SEND_GRID_PASS  // if you provide a valid SendGrid ApiKey
    );
    //with API KEY it may be
    // const transporterOptions = mailer.sendGridTransportOptions(apiKey)
    // API Keys must ALWAYS be provided as environment variables


    const prodSender = new mailer.create(transporterOptions);


      prodSender.send(mailOptions).then(mail=>{
        /* perform some operations when received mail info */})
      .catch(e=>console.log(e));//optionally do something on email failing
    }

The send method is based on nodemailer's sendMail method and it is asynchronous, so you should pay attention to not blocking the request-response cycle unnecessarily.

The HTML template

This section is about the buildHTML method

for both the template and the stylesheet, the user must provide the correct path to the files, hence, it is recommended to use __dirname and the path package when providing such paths.

// instead of:
const template =  'path/to/my/template.html'
const stylesheet =  'path/to/my/stylesheet.css'

//use:
const template =  path.join(__dirname,'path','to','my','template.html');
const stylesheet =  path.join(__dirname,'path','to','my','stylesheet.css');

You can optionally provide an interpolation token that will be used as slot for data on parsing.

const html = await mailer.buildHTML(template,data,{styles, interpolation: '{{}}'})
// By default, the provided interpolation token is `{{}}`

The HTML will be parsed as string, so you need to take into account where this token will be provided:

With: template = <div>my name is {{}}</div> data = ['Mr.Bob','Jones'] it will be parsed as: <div>my name is Mr.Bob</div> And the rest of data will be ignored.