Aprenda Reaccionar construyendo un generador de memes

Los memes son geniales, son una forma muy divertida de describir ideas y opiniones. Así que no es una coincidencia que haya elegido una aplicación generadora de memes como proyecto final en mi curso gratuito de React en Scrimba. La aplicación funciona extrayendo una imagen de meme aleatoria de una API y colocando su texto en la parte superior para crear su propio meme personalizado.

Entonces, en este artículo, le daré una guía paso a paso para crear la aplicación. Si alguna vez se confunde, también puede seguir estos pasos en el curso de Scrimba, comenzando en esta lección.

Y luego, si le gusta mi estilo de enseñanza y está de humor para un desafío más difícil después de completar este tutorial, consulte mi próximo curso avanzado sobre Scrimba.

Nota: Ya debería estar bastante familiarizado con algunos de los conceptos fundamentales de React, como componentes, estado, accesorios y métodos de ciclo de vida. Además, este tutorial no usa Hooks, pero en mi próximo curso cubriremos Hooks en profundidad y obtendremos toneladas de práctica usándolos.

1. Crear el texto estándar y renderizar un componente de la aplicación

Crear la tarea repetitiva

Lo primero que debemos hacer es crear el código repetitivo de la aplicación. Para hacer esto, importamos Reacty ReactDOMusamos ReactDOMpara renderizar un componente llamado App, que crearemos más adelante. Luego colocamos el Appcomponente en la 'raíz'. También importamos Appde su archivo "./App", que crearemos en breve.

// index.js import React from 'react'; import ReactDOM from 'react-dom'; import App from './App'; ReactDOM.render(, document.getElementById('root')); 

Luego creamos nuestro App.jsarchivo. En él, creamos un componente funcional llamado Appque, por ahora, devuelve un simple

. Luego lo exportamos. los

nos permite comprobar que la aplicación se muestra correctamente en la pantalla.

import React from 'react'; function App() { return 

Hello world!

; } export default App;

El resultado resultante es este:

Hola mundo renderizado

2. Creación de los componentes Header y MemeGenerator

Creación de la tarea Header y MemeGenerator

A continuación, creamos los componentes Header y MemeGenerator. El encabezado solo mostrará elementos, mientras que MemeGenerator llamará a la API y retendrá los datos en su estado.

Comencemos por crear el Header.jsarchivo. Dado que el encabezado es un componente que solo se usa para mostrar, debe ser un componente funcional. Por ahora, el componente debería devolver un simple

. Después de crearlo, exportamos Header.

import React from 'react'; function Header() { return 

HEADER

; } export default Header;

A continuación, creamos el MemeGenerator.jsarchivo. Como el MemeGeneratorcomponente almacenará datos y realizará llamadas a una API, debe ser un componente de clase. Todavía necesitamos importar React, y dado que será un componente de clase, también lo importaremos Component(que es una importación con nombre).

MemeGenerator necesita un constructor()which invoca super()y como mantendrá el estado, le agregamos un estado vacío ahora. Como en el componente Encabezado, renderizamos un simple

para empezar. Luego exportamos MemeGenerator.

import React, { Component } from 'react'; class MemeGenerator extends Component { constructor() { super(); this.state = {}; //empty state } render() { return 

MEME GENERATOR SECTION

; } } export default MemeGenerator;

Ahora, importamos Header y MemeGenerator App.jsy creamos una instancia de cada uno en nuestro componente App. Para mostrar los componentes correctamente, los envolvemos en un .

import React from 'react'; import Header from './Header'; import MemeGenerator from './MemeGenerator'; function App() { return ( ); } export default App; 

3. Completando el componente Encabezado.

To complete the component, we add a trollface image by inserting an tag and setting the src to the image's URL. We then add a

tag with the name of our app and wrap them both in the semantic HTML5 tag.

function Header() { return (  Problem?

Meme Generator

); }

As styling is outside the scope of this course, the CSS styles have already been created and applied to the tag. The result is this:

Encabezado renderizado

That said, learners can always play around with the styling and hone their CSS skills by themselves. With the now complete, the rest of the challenge will take place in

4. Initializing state

Inicializando tarea de estado

We now have to initialize state so that it saves a top text, a bottom text and a random image, which is already supplied.

To do this, we build up the empty object we placed in the when we originally built it. We initialize topText and bottomText as empty strings and randomImg as the provided URL.

class MemeGenerator extends Component { constructor() { super(); this.state = { topText: '', bottomText: '', randomImg: '//i.imgflip.com/1bij.jpg' }; } } 

5. Making the API call

Realizar la tarea de llamada a la API

Next, we make an API call to the provided URL and save the data returned (which is an array found in response.data.memes) to a new state property called allMemeImgs.

When we need to load data from an endpoint to use in our component, a good place to make the request is the componentDidMount() lifecycle method. As soon as the component mounts, we use the native fetch() function to call to the provided URL.

componentDidMount() { fetch("//api.imgflip.com/get_memes") } 

This returns a promise which we turn into a Javascript object with the .json() method.

componentDidMount() { fetch("//api.imgflip.com/get_memes") .then(response => response.json()) } 

Then we get the response which is useful to us by pulling the memes array from response.data.

componentDidMount() { fetch("//api.imgflip.com/get_memes") .then(response => response.json()) .then(response => { const { memes } = response.data }) } 

Now, we save the results to a new state property called allMemeImgs. To do this, we initialize allMemeImgs as an empty array.

this.state = { topText: '', bottomText: '', randomImg: '//i.imgflip.com/1bij.jpg', allMemeImgs: [] }; 

Now, back in componentDidMount(), we set state. As we are not interested in what the previous state was, we set allMemeImgs to memes.

componentDidMount() { fetch("//api.imgflip.com/get_memes") .then(response => response.json()) .then(response => { const { memes } = response.data this.setState({ allMemeImgs: memes }) }) } 

To ensure that it works, we console.log the first item, which looks something like this:

salida de console.log

Here's an overview of the entire componentDidMount() function.

componentDidMount() { //ensure that data is fetched at the beginning fetch("//api.imgflip.com/get_memes") //call to URL .then(response => response.json()) //turn promise into JS object .then(response => { const { memes } = response.data //pull memes array from response.data console.log(memes[0]) // check data is present this.setState({ allMemeImgs: memes }) // set allMemeImgs state }) } 

6. Creating the input form

We now want to create a form which will eventually allow the user to input the top and bottom texts. We do this with an HTML tag and a simple which says 'Gen'. We style it with the pre-provided CSS.

render() { return ( Gen ) } 

Botón de generación renderizada

7. Adding input fields to the form

Tarea Agregar campos de entrada

Next, it is up to us to add the two input fields (one for the top text and one for the bottom text). The form should be a controlled form, so we will need to add all the attributes needed in order for that to work. We will create the onChange handler later.

We create two input fields which both have the type text and appropriate name attributes (topText and bottomText). Rather than using labels, we use placeholders: 'Top Text' and 'Bottom Text'.

Lastly, in order to make this a controlled form, we set the value as equal to the current value in state with {this.state.topText} and {this.state.bottomText}.

render() { return ( Gen ) } 

8. Creating the onChange handler.

Creación de la tarea del controlador onChange

Now, we create the onChange handler, which will update the corresponding state on every change of the input field.

First, we create a handleChange() function which receives an event.

handleChange(event) { } 

Now, we set the onChange of both input fields to equal handleChange.

   Gen  

We need to remember to bind the method in the constructor — a common gotcha for React developers.

constructor() { super() this.state = { topText: "", bottomText: "", randomImg: "//i.imgflip.com/1bij.jpg", allMemeImgs: [] } this.handleChange = this.handleChange.bind(this) } 

To test the new handleChange() function, we add a simple console.log:

handleChange(event) { console.log("Working!") } 

If it is correctly firing, you'll see something like this:

Console.log renderizado (

Now to fill in the handleChange() function. To do this, we want to pull the name and value properties from event.target so that we can get the name of the state we are supposed to update (topText or bottomText) and the value which is typed into the box.

handleChange(event) { const { name, value } = event.target } 

We will now use these to update state. As we are not interested in what the previous state was, we can just provide an object in which we set the [name] to the value typed into the input field.

handleChange(event) { const {name, value} = event.target this.setState({ [name]: value }) } 

9. Displaying a meme image alongside the top and bottom text

We now want the app to display a meme image alongside the top and bottom text. We insert an tag underneath the and set the randomImg which we initialized as its source by using src={this.state.randomImg}. We then add two

tags which display the corresponding text which is also saved in state. All of this is wrapped in a div and styled with the pre-provided meme class.

{this.state.topText}

{this.state.bottomText}

We can now test the app by typing into the text boxes. As state is being correctly set on every keystroke, the text displayed on the image changes each time we type.

Representa un ejemplo de progreso hasta ahora

10. Displaying a random meme image alongside the Top and Bottom text

Visualización de una tarea de imagen de meme aleatoria

Now, we need to create a method which displays a meme image which it randomly chooses from our allMemeImgs array when the Gen button is clicked. The property on the chosen image in the array is .url.

We can break this task down into smaller parts.

Firstly, we set the form's onSubmit to equal the name of our new method, which we will call handleSubmit().

We now create the handleSubmit() function above the render() function. We need to preventDefault on the event, otherwise, the method will try to refresh the page.

handleSubmit(event) { event.preventDefault() } 

We also need to bind handleSubmit() in our constructor().

constructor() { super() this.state = { topText: "", bottomText: "", randomImg: "//i.imgflip.com/1bij.jpg", allMemeImgs: [] } this.handleChange = this.handleChange.bind(this) this.handleSubmit = this.handleSubmit.bind(this) } 

Now, we need to get a random number, get the meme from that index and set randomImg to the .url of the random item.

handleSubmit(event) { event.preventDefault() // get a random int (index in the array) // get the meme from that index // set `randomImg` to the `.url` of the random item I grabbed } 

To get a random number, we use Math.floor(Math.random). To make sure that it is one of the indices in our allMemeImgs array, we multiply by the length of the array.

const randNum = Math.floor(Math.random() * this.state.allMemeImgs.length); 

We now set randMemeImg to equal allMemeImgs, with the index of allMemeImgs as the randNum we just got. We then add .url to the end of it.

const randMemeImg = this.state.allMemeImgs[randNum].url; 

Now, all we need to do is update the state by updating the randomImg property with randMemeImg.

this.setState({ randomImg: randMemeImg }); 

Our completed handleSubmit() function looks like this:

handleSubmit(event) { event.preventDefault() const randNum = Math.floor(Math.random() * this.state.allMemeImgs.length) const randMemeImg = this.state.allMemeImgs[randNum].url this.setState({ randomImg: randMemeImg }) } 

Completed Meme Generator

Aplicación de trabajo

We now have completed the meme generator app, and get a different image every time we hit the Gen button, which is then overlaid with the text we input.

Para ampliar nuestro aprendizaje, podríamos jugar con el código y ver si podemos mejorarlo, o intentar obtener imágenes de una API diferente. Para una práctica realmente dura, incluso podríamos eliminar todo el código e intentar compilarlo nuevamente desde cero.

Felicitaciones por seguir el tutorial y aprender todas las habilidades utilizadas en este proyecto.

Y si está listo para ello, consulte mi próximo curso avanzado, ¡ya que lo llevará a un nivel profesional en React!