Javascript

There’s nothing as flashy and useful for JavaScript interviews than recursion. If you just want to be impressive with recursion in JavaScript, here are some semi real-world (technical test type) examples. The short definition of a recursive solution to a problem (in computer science) is: don’t use iteration. This usually means a function has to call itself with a smaller instance of the same problem until it hits a trivial case (usually defined in the problem). ...

Writing multiple components in one file is a pattern from React where some files contain multiple components. Some of those components are “private” to the file/exported component since no other component needs to consume them. ...

In “Using ES6 classes for Sequelize 4 models” we explored how to define Sequelize models using ES6 classes. One of the benefits of such an approach is that it allows easy unit testing, it allows you to instantiate the model without the baggage of all of Sequelize (and/or a database). The examples will use Jest module auto-mocking but should be portable to other module mocking libraries (eg. Proxyquire) with some modifications. ...

An email sending example. ...

An example consuming a GraphQL API in JavaScript from Node and the browser using graphql.js ...

Parcel allows us to bundle frontend applications with no configuration and GitHub pages affords us a way to deploy them for free. Here’s how to use these two tools together to deploy a JavaScript application. Full example of a repo deployed like this: https://github.com/HugoDF/js-graphql-client-example, and see https://codewithhugo.com/js-graphql-client-example/. Or the repo with the demos: https://github.com/HugoDF/parcel-gh-pages-deploy and see https://codewithhugo.com/parcel-gh-pages-deploy/. ...

There’s some nice use-cases for snapshot tests outside of the well-travelled React/Vue UI component ones. In other words, although React and Vue testing with snapshots is pretty well documented, that’s not the only place they’re useful. As a rule of thumb, you could replace a lot of unit tests that assert on with specific data with snapshot tests. We have the following pros for snapshot tests: - the match data is stored in a separate file so it’s harder to lose track of things, eg. ...

There always comes a point in a web application’s life where an operation is best served in the background, this is where queues come in. There are a few queuing solutions in Node. None of them are ridiculously dominant, eg. Kue, RSMQ, Bee Queue, bull. The issue with Kue, RSMQ and Bee Queue was its use of a done callback as the recommended API. Bull https://github.com/OptimalBits/bull is a premium Queue package for handling jobs and messages in NodeJS. It’s backed by Redis and is pretty feature-rich. Most of all, it leverages a Promise-based processing API which means async/await. We’ll walk through an application that sends webhooks with a given payload to a set of URLs. ...

When using docker-compose, it’s good practice to make anything that relies on Postgres wait for it to be up before launching. This avoids connection issues inside the app. This post walks through how to deliver this functionality both as a CLI and a module that works both as a CommonJS module (require) and ES modules, without transpilation. “A fast, production ready, zero-dependency ES module loader for Node 6+!” is esm’s promise. From this sample project, it’s worked. ...

Here is the implementation for a function that takes a Promise-based fetch function and a function that decides if a response has been successful (from a polling perspective) and polls the fetch function until the isSuccess function returns true: ...