Introduction

In this lab, we will be creating a Closable Alert component using React. The component will allow users to display a message of a specific type and close the alert when they are done with it. By the end of this lab, you will have learned how to use the useState() and useEffect() hooks to create a dynamic component that can be easily customized to fit your needs.

Closable Alert

index.html and script.js have already been provided in the VM. In general, you only need to add code to script.js and style.css.

Renders an alert component with the type prop.

The Alert component takes in the following props:

• isDefaultShown: a boolean that determines if the alert is initially shown or not (default is false)
• timeout: a number that specifies the duration in milliseconds before the alert fades out (default is 250)
• type: a string that determines the type of alert (e.g. "warning", "error", "info")
• message: a string that contains the message to display in the alert

The component does the following:

• Uses the useState() hook to create the isShown and isLeaving state variables and sets both to false initially.
• Defines a timeoutId variable to keep the timer instance for clearing on component unmount.
• Uses the useEffect() hook to update the value of isShown to true and clear the interval by using timeoutId when the component is unmounted.
• Defines a closeAlert function to set the component as removed from the DOM by displaying a fading out animation and setting isShown to false via setTimeout().
• Renders the alert component if isShown is true. The component has the appropriate styles based on the type prop and fades out if isLeaving is true.

Here's the code:

@keyframes leave {
  0% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}

.alert {
  padding: 0.75rem 0.5rem;
  margin-bottom: 0.5rem;
  text-align: left;
  padding-right: 40px;
  border-radius: 4px;
  font-size: 16px;
  position: relative;
}

.alert.warning {
  color: #856404;
  background-color: #fff3cd;
  border-color: #ffeeba;
}

.alert.error {
  color: #721c24;
  background-color: #f8d7da;
  border-color: #f5c6cb;
}

.alert.leaving {
  animation: leave 0.5s forwards;
}

.alert .close {
  position: absolute;
  top: 0;
  right: 0;
  padding: 0 0.75rem;
  color: #333;
  border: 0;
  height: 100%;
  cursor: pointer;
  background: none;
  font-weight: 600;
  font-size: 16px;
}

.alert .close::after {
  content: "x";
}

const Alert = ({ isDefaultShown = false, timeout = 250, type, message }) => {
  const [isShown, setIsShown] = React.useState(isDefaultShown);
  const [isLeaving, setIsLeaving] = React.useState(false);

  let timeoutId = null;

  React.useEffect(() => {
    setIsShown(true);
    return () => {
      clearTimeout(timeoutId);
    };
  }, [isDefaultShown, timeout, timeoutId]);

  const closeAlert = () => {
    setIsLeaving(true);
    timeoutId = setTimeout(() => {
      setIsLeaving(false);
      setIsShown(false);
    }, timeout);
  };

  return (
    isShown && (
      <div
        className={`alert ${type} ${isLeaving ? "leaving" : ""}`}
        role="alert"
      >
        <button className="close" onClick={closeAlert} />
        {message}
      </div>
    )
  );
};

ReactDOM.createRoot(document.getElementById("root")).render(
  <Alert type="info" message="This is info" />
);

Please click on 'Go Live' in the bottom right corner to run the web service on port 8080. Then, you can refresh the Web 8080 Tab to preview the web page.

Summary

Congratulations! You have completed the Closable Alert lab. You can practice more labs in LabEx to improve your skills.

🚀 Practice Now: Create Closable React Alert

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