Category: React

Sometimes, we want to add a delay onMouseOver event handler with React.

In this article, we’ll look at how to add a delay onMouseOver event handler with React.

How to add a delay onMouseOver event handler with React?

To add a delay onMouseOver event handler with React, we can use the Lodash debounce function.

For instance, we write:

import React, { useState } from "react";
import { debounce } from "lodash";

export default function App() {
  const [isHovered, setIsHovered] = useState(false);
  console.log(isHovered);

  const debouncedHandleMouseEnter = debounce(() => setIsHovered(true), 500);

  const handlOnMouseLeave = () => {
    setIsHovered(false);
    debouncedHandleMouseEnter.cancel();
  };

  return (
    <div
      onMouseEnter={debouncedHandleMouseEnter}
      onMouseLeave={handlOnMouseLeave}
    >
      hover me
    </div>
  );
}

We defined the isHovered state with useState.

Then we define the debouncedHandleMouseEnter function by passing in the event handler function into Lodash’s debounce function.

We set the debounce delay to 500ms.

Next, we have the handlOnMouseLeave function where we call debouncedHandleMouseEnter.cancel to cancel the calling of the debouncedHandleMouseEnter function when handlOnMouseLeave is called.

Therefore, when we hover over the div, we see isHovered becomes true.

And when we move our mouse away from the div, isHovered becomes false.

Conclusion

To add a delay onMouseOver event handler with React, we can use the Lodash debounce function.

Sometimes, we want to render a HTML comment in React.

In this article, we’ll look at how to render a HTML comment in React

How to render a HTML comment in React?

To render a HTML comment in React, we can use the dangerouslySetInnerHTML prop.

For instance, we write:

import React from "react";

const ReactComment = ({ text }) => {
  return <div dangerouslySetInnerHTML={{ __html: `<!-- ${text} -->` }} />;
};

export default function App() {
  return <ReactComment text={"My beautiful HTML comment"} />;
}

We set dangerouslySetInnerHTML to an object that has the __html property set to a string with the HTML comment.

Then we should see the comment when we inspect the HTML code in the Elements tab of the dev console of our browser.

Conclusion

To render a HTML comment in React, we can use the dangerouslySetInnerHTML prop.

Sometimes, we want to map the children of a parent component in React.

In this article, we’ll look at how to map the children of a parent component in React.

Map the Children of a Parent Component in React

To map the children of a parent component in React, we can use the React.Children.map method.

For instance, we write:

import React from "react";

const Wrapper = ({ children }) => (
  <div style={{ color: "red" }}>{children}</div>
);

const OpaqueWrapper = ({ children }) =>
  Array.isArray(children) ? (
    <Wrapper>
      {React.Children.map(children, (child) =>
        React.cloneElement(child, {
          style: { ...child.props.style, opacity: 0.5 }
        })
      )}
    </Wrapper>
  ) : null;

export default function App() {
  return (
    <div>
      <OpaqueWrapper>
        <p style={{ fontWeight: "bold" }}>foo</p>
        <p>bar</p>
        <p>baz</p>
      </OpaqueWrapper>
    </div>
  );
}

We have the Wrapper that takes the children components and wrap them in a div.

And we set the color of the content to red.

Then we have the OpaqueWrapper that takes the children prop and calls the React.Children.map with children and a callback to return the components that we cloned with React.cloneElement.

During the processing of cloning, we set the style prop to merge the style prop in the original child component and combine it with opacity set to 0.5 with the spread operator.

Now we should see foo being red, bold and translucent and the rest of the text are red and translucent.

Conclusion

To map the children of a parent component in React, we can use the React.Children.map method.

Sometimes, we want to format a date inside a React component.

In this article, we’ll look at how to format a date inside a React component.

Format a Date Inside a React component

To format a date inside a React component, we can use the toLocaleDateString method.

For instance, we write:

import React from "react";

const DATE_OPTIONS = {
  weekday: "short",
  year: "numeric",
  month: "short",
  day: "numeric"
};

export default function App() {
  return (
    <div>{new Date(2021, 1, 1).toLocaleDateString("en-US", DATE_OPTIONS)}</div>
  );
}

We have the DATE_OPTIONS object with the weekdayproperty set to‘short’` to show the abbreviation of the day of the week.

year is set to 'numeric' to show the year as a 4 digit number.

month is set to 'short' to show the abbreviation of the month.

And year is set to 'numeric' to show the year as a number.

Then we call toLocaleDateString with the locale string and the DATE_OPTIONS object to return the date string formatted with the specified format options.

As a result, we see:

Mon, Feb 1, 2021

displayed on the screen.

Conclusion

To format a date inside a React component, we can use the toLocaleDateString method.