Memi su izvrsni - tako su zabavan način opisivanja ideja i mišljenja. Stoga nije slučajno što sam odabrao aplikaciju za stvaranje memea kao glavni kamen u svom besplatnom tečaju React na Scrimbi. Aplikacija radi povlačenjem slučajne meme slike iz API-ja i postavljanjem teksta iznad nje da bi se stvorio vaš vlastiti, personalizirani mem.

Dakle, u ovom članku dat ću vam detaljni vodič za stvaranje aplikacije. Ako se ikad zbunite, također možete slijediti ove korake u tečaju Scrimba, počevši od ovog predavanja.

A onda, ako vam se sviđa moj stil poučavanja i ako ste raspoloženi za teži izazov nakon što završite ovaj tutorial, pogledajte moj nadolazeći tečaj o Scrimbi.

Napomena: Već biste trebali biti prilično upoznati s nekim temeljnim konceptima React-a, poput komponenata, stanja, rekvizita i metoda životnog ciklusa. Također, ovaj vodič ne koristi Kuke, ali u mom nadolazećem tečaju detaljno ćemo obraditi Kuke i dobiti puno vježbi kako ih koristiti.

1. Izrada uzorka i prikazivanje komponente aplikacije

Prvo što moramo učiniti je stvoriti šifru uzorka za aplikaciju. Da bismo to učinili, uvozimo Reacti ReactDOMkoristimo ReactDOMza generiranje komponente koja se zove Appi koju ćemo kasnije stvoriti. Zatim Appkomponentu stavljamo u 'korijen'. Također uvozimo Appiz njegove datoteke "./App"koju ćemo uskoro stvoriti.

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

Zatim kreiramo našu App.jsdatoteku. U njemu kreiramo funkcionalnu komponentu Appkoja se za sada vraća jednostavna

. Zatim ga izvozimo. The

omogućuje nam da provjerimo prikazuje li se aplikacija ispravno na zaslonu.

import React from 'react'; function App() { return 
Hello world!
; } export default App; 

Rezultat je sljedeći:

2. Izrada komponenata Header i MemeGenerator

Dalje kreiramo komponente Header i MemeGenerator. Zaglavlje će prikazati samo elemente, dok će MemeGenerator pozvati API i zadržati podatke u stanju.

Krenimo s izradom Header.jsdatoteke. Budući da je Header komponenta koja se koristi samo za prikaz, ona bi trebala biti funkcionalna komponenta. Za sada bi komponenta trebala vratiti jednostavan

. Nakon stvaranja, zatim izvozimo Header.

import React from 'react'; function Header() { return 
HEADER
; } export default Header; 

Dalje kreiramo MemeGenerator.jsdatoteku. Budući da MemeGeneratorće komponenta držati podatke i pozivati ​​API, to mora biti komponenta klase. Još uvijek moramo uvesti React, a budući da će to biti komponenta klase, uvest ćemo Componenti (što je imenovani import).

MemeGenerator treba constructor()koji pozivi super()i kako će biti u stanju čekanja, sada mu dodajemo neko prazno stanje. Kao u komponenti Header, i mi pružamo jednostavan

za početak. Zatim izvozimo MemeGenerator.

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

Sada uvozimo i Header i MemeGenerator u App.jssvaki od njih i stvaramo primjerak u našoj komponenti aplikacije. Kako bismo pravilno prikazali komponente, omotamo ih u .

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

3. Dovršavanje komponente Header.

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 (  
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:

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

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

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:

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 ) } 

7. Adding input fields to the form

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.

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:

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.

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

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

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.

Za daljnje učenje mogli bismo se igrati s kodom i vidjeti možemo li ga poboljšati ili pokušati dobiti slike iz drugog API-ja. Za neke vrlo zahtjevne prakse mogli bismo čak izbrisati sav kôd i pokušati ga ponovno napraviti od nule.

Čestitamo vam što ste slijedili tutorial i naučili sve vještine korištene u ovom projektu.

A ako ste spremni za to, pogledajte moj nadolazeći tečaj jer će vas odvesti na profesionalnu razinu u Reactu!