Category: React Answers

Sometimes, we want to dynamically load a stylesheet with React.

In this article, we’ll look at how to dynamically load a stylesheet with React.

Dynamically Load a Stylesheet with React

To dynamically load a stylesheet with React, we can add a link element with the attributes we want.

For instance, we write:

import React, { useState } from "react";

export default function App() {
  const [stylePath] = useState(
    "https://cdn.jsdelivr.net/npm/bootstrap@5.1.1/dist/css/bootstrap.min.css"
  );

  return (
    <div>
      <link rel="stylesheet" type="text/css" href={stylePath} />
    </div>
  );
}

to create the stylePath state with the useState hook.

Its initial value is set to the URL of the stylesheet that we want to include.

Then we add a link element with the href prop set to stylePath to add the stylesheet at the given URL into the component.

Conclusion

To dynamically load a stylesheet with React, we can add a link element with the attributes we want.

Sometimes, we want to map only a portion of an array to components in a React component.

In this article, we’ll look at how to map only a portion of an array to components in a React component.

Map Only a Portion of an Array to Components in a React Component

To map only a portion of an array to components in a React component, we can use the JavaScript array’s filter method to return an array of the items we want to map before calling map.

For instance, we write:

import React from "react";

export default function App() {
  const feed = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

  return (
    <div>
      {feed
        .filter((item) => item <= 5)
        .map((filteredItem) => (
          <p key={filteredItem}>{filteredItem}</p>
        ))}
    </div>
  );
}

to create the feed array.

And we want to display the first 5 entries from feed.

To do this, we call filter with (item) => item <= 5 to return the first 5 elements.

Then we call map with a callback to return p elements with the content of the elements to display them on the screen.

Now we see:

1

2

3

4

5

on the screen

Conclusion

To map only a portion of an array to components in a React component, we can use the JavaScript array’s filter method to return an array of the items we want to map before calling map.

Sometimes, we want to turn an SVG string into an image in a React component.

In this article, we’ll look at how to turn an SVG string into an image in a React component.

Turn an SVG String into an Image in a React Component

To turn an SVG string into an image in a React component, we can put the SVG string in a base64 URL string.

Then we can use the base64 URL string as the URL of the image.

For instance, we write:

import React from "react";

export default function App() {
  const image =
    '<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny" width="47.4" height="40.65" viewBox="21 18.5 158 135.5"><path d="M25,50 l150,0 0,100 -150,0 z" stroke-width="4" stroke="black" fill="rgb(128,224,255)" fill-opacity="1" ></path><path d="M25,50 L175,150 M25,150 L175,50" stroke-width="4" stroke="black" fill="black" ></path><g transform="translate(0,0)" stroke-width="4" stroke="black" fill="none" ><circle cx="100" cy="30" r="7.5" fill="black" ></circle><circle cx="70" cy="30" r="7.5" fill="black" ></circle><circle cx="130" cy="30" r="7.5" fill="black" ></circle></g></svg>';

  return (
    <div>
      <img src={`data:image/svg+xml;utf8,${image}`} />
    </div>
  );
}

to assign the image variable to a SVG string.

Then we set the src prop to a base64 URL that has the image string in it.

Now we should see the SVG displayed on the screen.

Conclusion

To turn an SVG string into an image in a React component, we can put the SVG string in a base64 URL string.

Then we can use the base64 URL string as the URL of the image.

Sometimes, we want to add a background video with React.

In this article, we’ll look at how to add a background video with React.

Add a Background Video with React

To add a background video with React, we can add the video element with the autoPlay prop.

For instance, we write:

import React from "react";

export default function App() {
  return (
    <div>
      <video loop autoPlay>
        <source
          src="https://file-examples-com.github.io/uploads/2017/04/file_example_MP4_480_1_5MG.mp4"
          type="video/mp4"
        />
        Your browser does not support the video tag.
      </video>
    </div>
  );
}

We add the video element with the loop prop to make the video replay after it’s finished.

And the autoPlay prop makes the video start automatically when we load the page.

Conclusion

To add a background video with React, we can add the video element with the autoPlay prop.

Sometimes, we want to check know when a React ref.current value has changed.

In this article, we’ll look at how to check know when a React ref.current value has changed.

Check Know When a React ref.current Value Has Changed

To check know when a React ref.current value has changed, we can add a callback ref to watch for the ref’s value with a function.

For instance, we write:

import React, { useCallback, useState } from "react";

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

  const onRefChange = useCallback(
    (node) => {
      console.log(node);
    },
    [count]
  );

  return (
    <div>
      <button onClick={() => setCount((c) => c + 1)}>increment</button>
      <p ref={onRefChange}>{count}</p>
    </div>
  );
}

We call the useCallback hook with a function that takes the node parameter.

node is the ref.current value since we pass the returned callback as the value of the ref prop.

We set count as the value to watch in the 2nd argument of useCallback.

Now when we update the count by clicking the button, the useCallback callback should be called.

And we see the node‘s value logged in the console after each change of count.

node is the p element with the latest value of count since we’re watching count‘s value as specified in the 2nd argument of useCallback.

Conclusion

To check know when a React ref.current value has changed, we can add a callback ref to watch for the ref’s value with a function.