66 lines
2.2 KiB
Markdown
66 lines
2.2 KiB
Markdown
---
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title: HS(D)P
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description: Describing the architecture of Handlers, Services, (Domains), and Presentation
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date: 2024-08-11
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tags:
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- development
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- javascript
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- typescript
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- hono
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slug: hsdp
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draft: true
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---
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## Handlers, Services, (Domains?), Presentation
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In [my last blog post](https://davesmithhayes.com/posts/fullstack-hono) I talked about how I have stopped thinking of my Node.js applications as Model-View-Controller and started thinking of the applications in a new, fun acronym: Handlers, Services, (_sometimes Domains_), and Prfesentation. I thought this would be a good topic for a new blog post. So here it is.
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I am going to be talking about this pattern in relationship to JavaScript and why the language lends itself to the pattern when working on applications.
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## The Application
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Like the previous post, I talked about building this blog with Bun and Hono. I am going to do the same here, however the application we are going to build is the all time classic - The TODO Application.
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## JavaScript
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One of the important things about JavaScript that alluded me for far too long was how the modules actually worked with Node.js. A module before ES6 was simply a JavaScript file that declares a `module.exports` value with the code you want to expose to other modules with the `require` function. Like so:
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```js
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function doSomething() {
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// ...
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}
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module.exports = doSomething;
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```
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_`example.js`_
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Then we can pull in `doSomething` with `require`:
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```js
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const doSomething = require('./example');
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```
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_`index.js`_
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I don't know why I didn't know this, but the code in the `example.js` file is evaluated **and** run during the `require()` call.
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In my past life I would try and build a Singleton class for holding onto an application's Connection Pool to a database. But because of how the Modules in Node.js work, we only need to instantiate the Pool and export it. Here's an example of how we can set up a single pool using the MariaDB official package:
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```js
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const mariadb = require('mariadb');
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const config = { ... };
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const pool = mariadb.createPool(config);
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module.eports = pool;
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```
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_`pool.js`_
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Now the connection pool is only created once and you can require this
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