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Abayomi Ogunnusi
Abayomi Ogunnusi

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React: Conditional rendering

This is one of the concepts I found most confusing when I started React. This post is a simple demonstration of how to render components with react using conditional rendering.

Let's get to it

它 Create a react project using npx create-react-app .
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它 Then start the react app using this command: npm start, this opens up the react page on the default localhost:3000
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Clean Up

Next, we cleanup our src folder and just have a h1 tag inside the App.jsthat says Choose your favorite pet.

import logo from "./logo.svg";
import "./App.css";

function App() {
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
    </div>
  );
}

export default App;
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它 Let's give this a well.
Our result:
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它 Next, we create a component folder and a file, I call it Choose.jsx. You can call it whatever you like.

  • Create a component
import React from "react";

export const Choose = () => {
  return (
    <div>
      <p>I am a cute Dog</p>
      <img
        src="https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.countryliving.com%2Flife%2Fkids-pets%2Fnews%2Fa44032%2Fdog-owners-take-more-pictures-of-their-pet-than-their-spouse%2F&psig=AOvVaw1qbUbk4x640915cLFiHmZ0&ust=1642064745637000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCMDU14Duq_UCFQAAAAAdAAAAABAJ"
        alt="cute dog"
      />
    </div>
  );
};
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它 Now let's import our Choose.jsx into the App.js component.

import "./App.css";
import { Choose } from "./components/Choose";

function App() {
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
      <Choose />
    </div>
  );
}

export default App;
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You should have the following on save:


它 Now let's write the logic that toggles our dog into a cat.
import useState Hook and declare an initial value for your useState.

import { useState } from "react";
import "./App.css";
import { Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false)
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
      <Choose />
    </div>
  );
}

export default App;
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它 Next, we create a button with an onClick function, and we tell it to change the setToggle state to true

import { useState } from "react";
import "./App.css";
import { Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false);
  return (
    <div className="App">
      <button onClick={() => setIsToggle(!toggle)}>Change</button>
      <h1>Choose your favorite pet</h1>
      <Choose />
    </div>
  );
}

export default App;

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它 Now, whenever we click our button, the value of our toggle is set to the inverse of its initial value.
Let me show you how this works by adding a console.log to the isToggle variable.

import { useState } from "react";
import "./App.css";
import { Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false);
  return (
    <div className="App">
      <button onClick={() => setIsToggle(!toggle)}>Change</button>
      {console.log(toggle)}
      <h1>Choose your favorite pet</h1>
      <Choose />
    </div>
  );
}

export default App;
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它 If you open your developer console by pressing f12 or use the inspect we have:
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Now, using ternary operators, let's build a conditional rendering that says, "Render my lovely dog or give me a cat."

Method 1: Inline If with Logical && Operator

import { useState } from "react";
import "./App.css";
import { Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false);
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
      <button onClick={() => setIsToggle(!toggle)}>Change</button>
      {toggle && <Choose />}
    </div>
  );
}

export default App;
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Explanation:

{toggle && <Choose />} this means if toggle is true, render component.

Method 2: Inline If-Else with Conditional Operator

Let's bring our cat into the picture by declaring that if we can't choose between a dog and a cat, we'll take a cat.

In the Choose.jsx file, quickly develop and export a working component.

export const Cat = () => {
  return (
    <div>
      <p>I am a cute Cat</p>
      <img
        src="https://th-thumbnailer.cdn-si-edu.com/ZoiTX0zdWNy5LOUC6Yh-qQsDcsE=/fit-in/1072x0/filters:focal(1834x1782:1835x1783)/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/11/2c/112cfb7f-d73f-40d6-afab-7e05be7c7b73/andy_warhol_ch_6.jpg"
        alt="cute cat"
        width="500px"
        height="380x"
      />
    </div>
  );
};

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Now let's import it into our App.js

import { useState } from "react";
import "./App.css";
import { Cat, Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false);
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
      <button onClick={() => setIsToggle(!toggle)}>Change</button>
      <Cat />
      {toggle && <Choose />}
    </div>
  );
}

export default App;
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Our final code

import { useState } from "react";
import "./App.css";
import { Cat, Choose } from "./components/Choose";

function App() {
  const [toggle, setIsToggle] = useState(false);
  return (
    <div className="App">
      <h1>Choose your favorite pet</h1>
      <button onClick={() => setIsToggle(!toggle)}>Change</button>

      {toggle ? <Choose /> : <Cat />}
    </div>
  );
}

export default App;
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This is where the magic happens {toggle ? <Choose /> : <Cat />}.

Here, we are saying if toggle is true render which is our dog and if not render cat.

I hope you found this article useful.For reference, you can find the entire code here click. Thanks

Resources

React.

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