Author: John Au-Yeung

React is an easy to use JavaScript framework that lets us create front end apps.

In this article, we’ll look at how to create a search filter app with React and JavaScript.

Create the Project

We can create the React project with Create React App.

To install it, we run:

npx create-react-app search-filter

with NPM to create our React project.

Create the Search Filter App

To create the search filter app, we write:

import { useState, useMemo } from "react";

const images = [
  {
    url: "https://images.dog.ceo/breeds/affenpinscher/n02110627_4597.jpg",
    description: "affenpinscher"
  },
  {
    url: "https://images.dog.ceo/breeds/akita/Akita_Inu_dog.jpg",
    description: "akita"
  },
  {
    url: "https://images.dog.ceo/breeds/retriever-golden/n02099601_7771.jpg",
    description: "golden retriever"
  }
];

export default function App() {
  const [keyword, setKeyword] = useState();
  const filteredImages = useMemo(() => {
    if (!keyword) {
      return images;
    }
    return images.filter(({ description }) => description.includes(keyword));
  }, [keyword]);

  return (
    <div className="App">
      <input value={keyword} onChange={(e) => setKeyword(e.target.value)} />
      <br />
      {filteredImages.map((fi) => {
        return (
          <div key={fi.description}>
            <img
              src={fi.url}
              alt={fi.description}
              style={{ width: 200, height: 200 }}
            />
            <p>{fi.description}</p>
          </div>
        );
      })}
    </div>
  );
}

We have the images array, which we want to search with the input box.

In the App component, we add the keyword state, which we create by th useState hook.

Then we use the useMemo hook to compute the filteredImages value.

We add a callback that checks for the keyword value.

If there’s no keyword value, then we return the images array.

Otherwise, we return the images array items that have the description that includes the keyword .

The 2nd argument has an array with the keyword variable since we want to updated filteredImages according to the keyword value.

filtereddImages is only updated with keyword changes.

Then in the return statement, we add the input box.

We set the onChange handler to set the keyword state.

Then we render the filteredImage items with the map method.

Conclusion

We can add a search filter easily with React’s useMemo hook and JavaScript.

React is an easy to use JavaScript framework that lets us create front end apps.

In this article, we’ll look at how to image slider app with React and JavaScript.

Create the Project

We can create the React project with Create React App.

To install it, we run:

npx create-react-app image-slider

with NPM to create our React project.

Create the Image Slider App

To create the image slider app, we write:

import { useState } from "react";

const images = [
  "https://i.picsum.photos/id/1/200/300.jpg?hmac=jH5bDkLr6Tgy3oAg5khKCHeunZMHq0ehBZr6vGifPLY",
  "https://i.picsum.photos/id/2/200/300.jpg?hmac=HiDjvfge5yCzj935PIMj1qOf4KtvrfqWX3j4z1huDaU",
  "https://i.picsum.photos/id/3/200/300.jpg?hmac=o1-38H2y96Nm7qbRf8Aua54lF97OFQSHR41ATNErqFc"
];

export default function App() {
  const [index, setIndex] = useState(0);

  const next = () => {
    setIndex((i) => (i + 1) % images.length);
  };

  const prev = () => {
    setIndex((i) => (i - 1) % images.length);
  };

  return (
    <div className="App">
      <button onClick={prev}>&lt;</button>
      <img src={images[index]} alt="" />
      <button onClick={next}>&gt;</button>
    </div>
  );
}

We have 3 image URLs in the images array.

In the App component, we have the index state, which is set by setIndex .

We set its initial value to 0.

Then we have the next and prev functions to set the index by incrementing by 1 and then get the remainder of that by dividing by images.length .

This gets the index of the next image to show.

prev is similar except we subtract by 1 instead of add to get the index of the previous image.

We go back to the first one after we reach the last image and we’re clicking the next button.

And we show the last image after we reach the first image and click on the previous button.

Then we return JSX with buttons to call the next and prev functions when we click them.

We show the image in the img element.

We can also make an image slider that moves to the next slide automatically by writing:

import { useEffect, useState } from "react";

const images = [
  "https://i.picsum.photos/id/1/200/300.jpg?hmac=jH5bDkLr6Tgy3oAg5khKCHeunZMHq0ehBZr6vGifPLY",
  "https://i.picsum.photos/id/2/200/300.jpg?hmac=HiDjvfge5yCzj935PIMj1qOf4KtvrfqWX3j4z1huDaU",
  "https://i.picsum.photos/id/3/200/300.jpg?hmac=o1-38H2y96Nm7qbRf8Aua54lF97OFQSHR41ATNErqFc"
];

export default function App() {
  const [index, setIndex] = useState(0);

  const next = () => {
    setIndex((i) => (i + 1) % images.length);
  };

  useEffect(() => {
    const timer = setInterval(() => {
      next();
    }, 1000);
    return () => {
      clearInterval(timer);
    };
  }, []);
  return (
    <div className="App">
      <img src={images[index]} alt="" />
    </div>
  );
}

Most of the code is the same except that we removed the prev function.

And we added the useEffect hook with a callback that calls next every second with setInterval .

We return a callback to call clearIntveral to clear the timer when we unmount the component.

The empty array in the 2nd argument lets us run the useEffect callback only when we mount the component.

Conclusion

We can create an image slider easily with React and JavaScript.

React is an easy to use JavaScript framework that lets us create front end apps.

In this article, we’ll look at how to create a counter app with React and JavaScript.

Create the Project

We can create the React project with Create React App.

To install it, we run:

npx create-react-app counter

with NPM to create our React project.

Create the Counter App

To create the counter app, we write:

import { useState } from "react";

export default function App() {
  const [count, setCount] = useState(0);

  const increment = () => {
    setCount((c) => c + 1);
  };

  const decrement = () => {
    setCount((c) => c - 1);
  };

  return (
    <div className="App">
      <button onClick={increment}>increment</button>
      <button onClick={decrement}>decrement</button>
      <p>{count}</p>
    </div>
  );
}

We have the count state created by the useState hook.

We set the initial value to 0.

Then we have the increment and decrement functions to increase and decrease count by 1 respectively.

We pass in a function that has the current value of the count state as the parameter and return the new value in the setCount callbacks.

Then we have buttons that calls increment and decrement respectively when we click them.

And we display the count as the result of our clicks.

Conclusion

We can create a counter app with React and JavaScript.

React is an easy to use JavaScript framework that lets us create front end apps.

In this article, we’ll look at how to image slider app with React and JavaScript.

Create the Project

We can create the React project with Create React App.

To install it, we run:

npx create-react-app image-slider

with NPM to create our React project.

Create the Image Slider App

To create the image slider app, we write:

import { useState } from "react";

const images = [
  "https://i.picsum.photos/id/1/200/300.jpg?hmac=jH5bDkLr6Tgy3oAg5khKCHeunZMHq0ehBZr6vGifPLY",
  "https://i.picsum.photos/id/2/200/300.jpg?hmac=HiDjvfge5yCzj935PIMj1qOf4KtvrfqWX3j4z1huDaU",
  "https://i.picsum.photos/id/3/200/300.jpg?hmac=o1-38H2y96Nm7qbRf8Aua54lF97OFQSHR41ATNErqFc"
];

export default function App() {
  const [index, setIndex] = useState(0);

  const next = () => {
    setIndex((i) => (i + 1) % images.length);
  };

  const prev = () => {
    setIndex((i) => (i - 1) % images.length);
  };

  return (
    <div className="App">
      <button onClick={prev}>&lt;</button>
      <img src={images[index]} alt="" />
      <button onClick={next}>&gt;</button>
    </div>
  );
}

We have 3 image URLs in the images array.

In the App component, we have the index state, which is set by setIndex .

We set its initial value to 0.

Then we have the next and prev functions to set the index by incrementing by 1 and then get the remainder of that by dividing by images.length .

This gets the index of the next image to show.

prev is similar except we subtract by 1 instead of add to get the index of the previous image.

We go back to the first one after we reach the last image and we’re clicking the next button.

And we show the last image after we reach the first image and click on the previous button.

Then we return JSX with buttons to call the next and prev functions when we click them.

We show the image in the img element.

We can also make an image slider that moves to the next slide automatically by writing:

import { useEffect, useState } from "react";

const images = [
  "https://i.picsum.photos/id/1/200/300.jpg?hmac=jH5bDkLr6Tgy3oAg5khKCHeunZMHq0ehBZr6vGifPLY",
  "https://i.picsum.photos/id/2/200/300.jpg?hmac=HiDjvfge5yCzj935PIMj1qOf4KtvrfqWX3j4z1huDaU",
  "https://i.picsum.photos/id/3/200/300.jpg?hmac=o1-38H2y96Nm7qbRf8Aua54lF97OFQSHR41ATNErqFc"
];

export default function App() {
  const [index, setIndex] = useState(0);

  const next = () => {
    setIndex((i) => (i + 1) % images.length);
  };

  useEffect(() => {
    const timer = setInterval(() => {
      next();
    }, 1000);
    return () => {
      clearInterval(timer);
    };
  }, []);
  return (
    <div className="App">
      <img src={images[index]} alt="" />
    </div>
  );
}

Most of the code is the same except that we removed the prev function.

And we added the useEffect hook with a callback that calls next every second with setInterval .

We return a callback to call clearIntveral to clear the timer when we unmount the component.

The empty array in the 2nd argument lets us run the useEffect callback only when we mount the component.

Conclusion

We can create an image slider easily with React and JavaScript.