Los hooks son una adición útil a la API de React que nos permiten organizar parte de nuestra lógica y estado en componentes de función. ¿Cómo podemos construir un gancho personalizado y compartirlo con el resto del mundo?

• ¿Qué son los ganchos?
• ¿Por qué son geniales los ganchos personalizados?
• Que vamos a hacer
• Paso 0: nombrar su gancho
• Paso 1: configuración de su proyecto
• Paso 2: escribir su nuevo React Hook
• Paso 3: usando su gancho React en un ejemplo
• Paso 4: compilar su gancho y ejemplo de React
• Paso 5: Publicar su gancho de React en npm
• Más recursos sobre ganchos

¿Qué son los ganchos?

React hooks en términos simples son funciones. Cuando los incluye en su componente o dentro de otro gancho, le permiten hacer uso de los componentes internos de React y partes del ciclo de vida de React con ganchos nativos como useStatey useEffect.

No planeo hacer una inmersión profunda sobre los ganchos, pero puede consultar una introducción rápida con un ejemplo useStatey la introducción del equipo de React.

¿Por qué son geniales los ganchos personalizados?

Lo mejor de crear enlaces personalizados es que le permiten abstraer la lógica de sus componentes, lo que facilita su reutilización en varios componentes de su aplicación.

Por ejemplo, si desea crear un contador simple en el que use el estado de React para administrar el recuento actual. En lugar de tener el mismo useStateenlace en cada archivo de componente, puede crear esa lógica una vez en un useCounterenlace, lo que facilita el mantenimiento, la extensión y la eliminación de errores si surgen.

Que vamos a hacer

Para los propósitos de este artículo, lo mantendremos simple con un gancho básico. Por lo general, puede usar un gancho porque en lugar de una función típica, usa otros ganchos nativos que deben usarse dentro de los componentes de la función React. Nos quedaremos con algunas entradas y salidas básicas para simplificar las cosas.

Vamos a recrear este gancho de Placecage personalizado que hice, que le permite generar fácilmente URL de imágenes que puede usar como imágenes de marcador de posición.

Si no está familiarizado, Placecage es una API que le permite generar imágenes de Nic Cage como imágenes de marcador de posición para su sitio web. ¿Tonto? Si. ¿Divertido? ¡Absolutamente!

Pero si no eres fanático del trabajo de Nic, puedes cambiar fácilmente la URL por Fill Murray, que usa imágenes de Bill Murray o placeholder.com, que genera un fondo de color sólido simple con texto que muestra el tamaño de la imagen.

Paso 0: nombrar su gancho

Antes de saltar a nuestro código real, nuestro objetivo final es publicar este gancho. Si ese no es su objetivo, puede omitir este paso, pero para la publicación, queremos crear un nombre para nuestro gancho.

En nuestro caso, nuestro nombre de gancho será usePlaceCage. Ahora, con eso en mente, tenemos 2 formatos de nuestro nombre: uno en formato camelCase y otro en formato snake-case.

• camelCase: usePlaceCage
• serpiente-caso: use-placecage

El formato camelCase se utilizará para la función de gancho real, donde el nombre de la caja de la serpiente se utilizará para el nombre del paquete y algunas de las carpetas. Al crear el nombre, tenga en cuenta que el nombre del paquete debe ser único. Si ya existe un paquete con el mismo nombre en npmjs.com, no podrá utilizarlo.

Si aún no tiene un nombre, ¡está bien! Puedes usar tu propio nombre o algo en lo que puedas pensar, realmente no importa demasiado ya que en realidad solo estamos tratando de aprender a hacer esto. Si fuera yo, por ejemplo, usaría:

• camelCase: useColbysCoolHook
• caso-serpiente: use-colbyscoolhook

Pero solo para aclarar, para el resto de nuestro ejemplo, nos quedaremos con usePlaceCagey use-placecage.

Paso 1: configuración de su proyecto

Aunque puede configurar su proyecto como desee, vamos a ver cómo crear un nuevo gancho a partir de esta plantilla que creé.

La esperanza aquí es que podamos eliminar algunas de las partes dolorosas del proceso y ser productivos de inmediato con nuestro gancho personalizado. Sin embargo, no se preocupe, le explicaré lo que sucede en el camino.

Los requisitos aquí son git e yarn, ya que ayuda a proporcionar herramientas que facilitan el andamiaje de esta plantilla, como el uso de la función de espacios de trabajo para permitir que los scripts npm fáciles administren el código desde la raíz del proyecto. Si alguno de ellos es un factor decisivo, puede intentar descargar el repositorio a través del enlace de descarga y actualizarlo según sea necesario.

Clonando la plantilla de gancho de git

Para empezar, clonemos el repositorio de Github. En el siguiente comando, debe reemplazarlo use-my-custom-hookcon el nombre de su gancho, como use-cookieso use-mooncake.

git clone //github.com/colbyfayock/use-custom-hook use-my-custom-hook cd use-my-custom-hook 

Una vez que clone y navegue a esa carpeta, ahora debería ver 2 directorios: un exampledirectorio y un use-custom-hookdirectorio.

Esto le dará algunas cosas para comenzar:

• Un directorio de ganchos que incluirá la fuente de nuestro gancho
• Construye scripts que compilen nuestro gancho con babel
• Una página de ejemplo que importa nuestro gancho y crea una página de demostración simple con next.js

Ejecutando los scripts de configuración del gancho

Después de clonar con éxito el repositorio, queremos ejecutar los scripts de configuración que instalan las dependencias y actualizan el enlace al nombre que queremos.

yarn install && yarn setup 

Cuando se ejecute el script de configuración, hará algunas cosas:

• It will ask you for your name – this is used to update the LICENSE and the package's author name
• It will ask you for your hook's name in 2 variations – camelCase and snake-case - this will be used to update the name of the hook throughout the template and move files with that name to the correct location
• It will reset git – it will first remove the local .git folder, which contains the history from my template and reinitialize git with a fresh commit to start your new history in
• Finally, it will remove the setup script directory and remove the package dependencies that were only being used by those scripts

Starting the development server

Once the setup scripts finish running, you'll want to run:

yarn develop 

This runs a watch process on the hook source, building the hook locally each time a source file is changed, and running the example app server, where you can test the hook and make changes to the example pages.

With this all ready, we can get started!

Follow along with the commit!

Step 2: Writing your new React Hook

At this point, you should now have a new custom hook where you can make it do whatever you'd like. But since we're going to walk through rebuilding the usePlaceCage hook, let's start there.

The usePlaceCage hook does 1 simple thing from a high level view – it takes in a configuration object and returns a number of image URLs that you can then use for your app.

Just as a reminder, any time I mention usePlaceCage or use-placecage, you should use the hook name that you set up before.

A little bit about placecage.com

Placecage.com is a placeholder image service that does 1 thing. It takes a URL with a simple configuration and returns an image... of Nic Cage.

From the simplest use, the service uses a URL pattern as follows:

//www.placecage.com/200/300 

This would return an image with a width of 200 and height of 300.

Optionally, you can pass an additional URL parameter that defines the type of image:

//www.placecage.com/gif/200/300 

In this particular instance, our type is gif, so we'll receive a gif.

The different types available to use are:

• Nothing: calm
• g: gray
• c: crazy
• gif: gif

We'll use this to define how we set up configuration for our hook.

Defining our core generator function

To get started, we're going to copy over a function at the bottom of our use-placecage/src/usePlaceCage.js file, which allows us to generate an image URL, as well as a few constant definitions that we'll use in that function.

First, let's copy over our constants to the top of our usePlaceCage.js file:

const PLACECAGE_HOST = '//www.placecage.com/'; const TYPES = { calm: null, gray: 'g', crazy: 'c', gif: 'gif' }; const DEFAULT_TYPE = 'calm'; const ERROR_BASE = 'Failed to place Nick'; 

Here we:

• Define a host, which is the base URL of our image service.
• Define the available types, which we'll use in the configuration API. We set calm to null, because it's the default value which you get by not including it at all
• Our default type will be calm
• And we set an error base which is a consistent message when throwing an error

Then for our function, let's copy this at the bottom of our usePlaceCage.js file:

function generateCage(settings) { const { type = DEFAULT_TYPE, width = 200, height = 200, count = 1 } = settings; const config = []; if ( type !== DEFAULT_TYPE && TYPES[type] ) { config.push(TYPES[type]); } config.push(width, height); if ( isNaN(count) ) { throw new Error(`${ERROR_BASE}: Invalid count ${count}`); } return [...new Array(count)].map(() => `${PLACECAGE_HOST}${config.join('/')}`); } 

Walking through this code:

• We define a generateCage function which we'll use to generate our image URL
• We take in a settings object as an argument, which defines the configuration of our image URL. We'll be using the same parameters as we saw in our placecage.com URL
• We destructure those settings to make them available for us to use
• We have a few defaults here just to make it easier. Our default type will be defined by DEFAULT_TYPE along with a default width, height, and number of results we want to return
• We create a config array. We'll use this  to append all of the different configuration objects in our URL and finally join them together with a / essentially making a URL
• Before we push our config to that array, we check if it's a valid argument, by using the TYPES object to check against it. If it's valid, we push it to our config array
• We then push our width and height
• We do some type checking, if we don't have a valid number as the count, we throw an error, otherwise we'll get incorrect results
• Finally, we return a new array with the number of results requested, mapped to a URL creator, which uses PLACECAGE_HOST as our defined base URL, and with our config array joined by /

And if we were to test this function, it would look like this:

const cage = generateCage({ type: 'gif', width: 500, height: 500, count: 2 }); console.log(cage); // ['//www.placecage.com/gif/500/500', '//www.placecage.com/gif/500/500']

Using our function in the hook

So now that we have our generator function, let's actually use it in our hook!

Inside of the usePlaceCage function in the use-placecage/src/usePlaceCage.js file, we can add:

export default function usePlaceCage (settings = {}) { return generateCage(settings); } 

What this does it uses our generator function, takes in the settings that were passed into the hook, and returns that value from the hook.

Similar to our previous use example, if we were to use our hook, it would look like this:

const cage = usePlaceCage({ type: 'gif', width: 500, height: 500, count: 2 }); console.log(cage); // ['//www.placecage.com/gif/500/500', '//www.placecage.com/gif/500/500'] 

At this point, it does the same thing!

So now we have our hook, it serves as a function to generate image URLs for the placecage.com service. How can we actually use it?

Follow along with the commit!

Step 3: Using your React hook in an example

The good news about our template, is it already includes an example app that we can update to easily make use of our hook to both test and provide documentation for those who want to use it.

Setting up the hook

To get started, let's open up our example/pages/index.js file. Inside of this file you'll see the following:

const hookSettings = { message: 'Hello, custom hook!' } const { message } = usePlaceCage(hookSettings); 

This snippet is what was used by default in the template just for a proof of concept, so let's update that. We're going to use the same exact configuration as we did in Step 2:

const hookSettings = { type: 'gif', width: 500, height: 500, count: 2 } const cage = usePlaceCage(hookSettings); 

Again, we set up our settings object with the configuration for our hook and invoke our hook and set the value to the cage constant.

If we now console log that value our to our dev tools, we can see it working!

console.log('cage', cage); 

Note: If you get an error here about message, you  can comment that our or remove it under the Examples section.

Updating the example with our new hook configuration

If you scroll down to the Examples section, you'll notice that we have the same default hookSettings as above, so let's update that again to make sure our example is accurate.

{`const hookSettings = { type: 'gif', width: 500, height: 500, count: 2 } const cage = usePlaceCage(hookSettings);`} 

You'll also notice that we're no longer using the message variable. If you didn't remove it in the last step, we can now replace it under the Output heading with:

 { JSON.stringify(cage) } 
 { cage.map((img, i) =>)} 

We're doing 2 things here:

• Instead of showing the variable itself, we wrap it with JSON.stringify so that we can show the contents of the array
• We also use the map function to loop over our image URLs in the cage constant and create a new image element for each. This let's us preview the output instead of just seeing the values

And once you save and open your browser, you should now see your updated examples and output!

Other things you can do on that page

Before moving on, you can also update a few other things that will be important for your hooks page:

• Update the How to use section with instructions
• Add additional examples to make it easier for people to know what to do

A  few things are also automatically pulled in from the use-placecage/package.json file. You can either update them there to make it easier to maintain or you can replace them in the example page:

• name: Is used at the

  of the page

• description: Is used at the description under the

• repository.url: Used to include a link to the repository
• author: The name and url are used to include a link at the bottom of the page

Follow along with the commit!

Step 4: Compiling your React hook and Example

The way we can make our hook work easily as an npm module is to compile it for others to use. We're using babel to do this.

Though the publish process already does this for us automatically with the prepublishOnly script in use-placecage/package.json, we can manually compile our hook using the yarn build command from the root of the project.

Along with compiling the hook, running yarn build will also compile the example page, allowing you to upload it wherever you'd like. After running that command, you should see an output of static HTML files in the example/out directory.

If you're looking for a recommendation, Netlify makes it easy to connect your Github account and deploy the static site.

See the demo site deployed to Netlify!

Step 5: Publishing your React hook to npm

Finally, if you're happy with your hook, it's time to publish!

npm makes this part really easy. The only prerequisite you need to have an npm account. With that account, let's log in:

npm login 

Which will prompt you for your login credentials.

Next, let's navigate to our hook's directory, as our package configuration is there under use-placecage/package.json:

cd use-placecage 

Then, we can simply publish!

npm publish 

Keep in mind, that each package name needs to be unique. If you used use-placecage, it's already taken... by me. ?

But if you're successful, npm should build your hook and upload it to the package registry!

It will then be available on npm with the following pattern:

//www.npmjs.com/package/[package-name] 

So for use-placeage, it's available here: //www.npmjs.com/package/use-placecage

We now have a custom hook!

Yay ? if you followed along, you should now have created a custom hook and published it to npm.

Though this was a silly example using placecage.com, it gives us a good idea of how we can easily set this up.

You'll also notice that this specific example wasn't the best use case for a hooks, where we could have simply used a function. Typically, we'll want to use custom hooks to wrap functionality that can only live inside a React component, such as useState. To learn more about that, you can read one of my other articles about custom hooks.

However, this gave us a good basis to talk through the creation and configuration of our new hook!

More resources about hooks

• How to destructure the fundamentals of React Hooks (freecodecamp.org)
• Introducing Hooks (reactjs.org)
• Hooks API Reference (reactjs.org)

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