Alert react Code Snippet in 2025

Renders an alert component with type prop.

• Use the useState() hook to create the isShown and isLeaving state variables and set both to false initially.
• Define timeoutId to keep the timer instance for clearing on component unmount.
• Use the useEffect() hook to update the value of isShown to true and clear the interval by using timeoutId when the component is unmounted.
• Define a closeAlert function to set the component as removed from the DOM by displaying a fading out animation and set isShown to false via setTimeout().

@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.render(
  <Alert type="info" message="This is info" />,
  document.getElementById('root')
);