Category: javascript

I have been using Node.js with Express.js for just over a year now and Typescript for 8 months building and maintaining micro services for an SME business operating globally.

The project is at: https://github.com/daveKoala/typescript-api-starter.git

Of the 1/2 dozen I’ve created from scratch each has grown in sophistication. I now know what I want for each REST api service (in no real order):

• Node.js with Express.js
• Multiple environments
• Typescript
• Unit testing (with tests alongside the code and not in ./tests/ directory)
• External cache
• A ‘developer’ mode that restarts when saving
• Debugging so I don’t have to rely on console.log
• All end points versioned and documented
• Authentication and Authorisation middleware
• Custom errors
• Re-try connections if they initially fail
• Project auto saves and lints
• A CI/CD pipeline that runs test and checks for external package vulnerabilities.

I am nearly there…

Node.js, Express.js and Typescript. Not much to say about this that has not already been said.

Multiple Environments: This is a bit trickier as conventional wisdom is that env values are not stored within the repo. This makes perfect sense, however the projects I am working with have 3 people at most and keeping the env within the private repo lets us quickly create new services and keep all settings, pipelines etc together with minimal fuss. It was a decision we made as a group 18 months ago and has paid off. I know there will be eye rolling at this tho’.

Unit Testing: I using Mocha.js and Chai.js no real reason apart from it works for me. There are 2 specific requirements. The first being that test scripts sit alongside the code being tested and the second is the option to publish test results. This project does both.

External Cache: Middleware on routes that intercepts the request, hashes the url and body to make an ID then queries the cache. A null response passes the request to the controller and caches the results.

‘Developer mode’: Easy with Nodemon and scripts within the package.json file. There are a few other useful scripts including a “lazy script” that runs tests, linting, audits and a build process.

Debugging: I’ll leave that to Visual Studio Code and commit any settings files.

All end points versioned and documented: Using Swagger and OpenDoc to create nice api docs. Added advantage is that you can link/download to the OpenDocs JSON into Postman to create collections.

Versioning: I opted for the “version via the request header” approach. Why? I like that the urls don’t change and because it is strict. Strict as in, if you fail to request a version you get feedback telling you what you need to do. The main thing about versioning is declaring a contract and sticking to it.

Authentication and Authorisation: Separate middleware that can leverage different methods specified by the project.

Custom errors: Easy enough, create meaningful error messages and responses. They also accept plugins for external logging.

Re-try connections if they initially fail: Also known as a Circuit Breaker pattern.

Project auto saves and lints: Let Visual Studio handle this and commit settings to the project.

CI/CD Pipeline: Convention over configuration and making use of files like Azure Pipelines YAML files to describe and run CI/CD processes.

This is an ongoing project and can be found at: https://github.com/daveKoala/typescript-api-starter.git

Every time I have anything to do with manipulating dates in JavaScript I need to stop and refresh my memory. Yes, there are amazing packages from Moment.js and Date-fns.

But why should I import a library just to a few simple things?

Here are my notes on dates (it is not an exhaustive list).

Time zones

There are 24 time zones mix in that many also have day light saving which adds/subtracts an hour. When a country does this is not constant around the world and is not fixed

So, in JavaScript there are two times:

• Local = the time of the computer the code is running on
• UTC = roughly the same as Greenwich Mean Time (GMT)

Date methods in JavaScript return Local time

In practice

Here I need to create a date range array. The range covers 30 days

const autoDays = () => {
      const daysInThePast = 30;
      const today = new Date();
      const pastDate = new Date(today);
      pastDate.setDate(today.getDate() - daysInThePast);
      return [
        pastDate.toISOString().substring(0, 10),
        today.toISOString().substring(0, 10)
      ];
    }

Explanation

• Two ‘new Date()’ are used to avoid unwanted mutation
• ‘today.getDate()’ returns the number part of the date. E.g. 29 in 29th July 2020
• ‘pastDate.setDate(today.getDate() – daysInThePast)’ sets the date number. Notice how the number could be a negative or positive number. E.g. -10 or +36
• JavaScript will correct the date to make sense. E.g. 36th July would become 5th August

Problem: I have an object that has a field call modules that is and array of activities. Activities is itself a complex and many nested object. I need to hunt for activities by their IDs and replace, delete or insert between existing objects

// Replace object in collection
Object.keys(data.modules).forEach(modKey => {
  Object.keys(data.modules[modKey].activities).forEach(activityKey => {
    if (data.modules[modKey].activities[activityKey].id === newActivity.id) {
      data.modules[modKey].activities.splice(activityKey, 1, newActivity);
    }
  });
});

// Remove object in collection
Object.keys(data.modules).forEach(modKey => {
  Object.keys(data.modules[modKey].activities).forEach(activityKey => {
    if (
      data.modules[modKey].activities[activityKey] &&
      data.modules[modKey].activities[activityKey].id === newActivity.id
    ) {
      data.modules[modKey].activities.splice(activityKey, 1);
    }
  });
});

// Insert object at index
const moudleIndex = 0;
const activityIndex = 2;

Object.keys(data.modules).forEach(modKey => {
  if (modKey == moudleIndex) {
    Object.keys(data.modules[modKey].activities).forEach(activityKey => {
      if (activityKey == activityIndex) {
        data.modules[modKey].activities.splice(activityKey, 0, newActivity);
      }
    });
  }
});