30秒学会 React 片段 – Alert

Creates an alert component with type prop.

• Define appropriate CSS styles and animations for the component’s elements.
• Use the React.setState() hook to create the isShown and isLeaving state variables and set their values to false.
• Define timeoutId to keep the timer instance for clearing on component unmount.
• Use the React.setEffect() hook to update the value of isShown to true and clear interval by using timeoutId when component is unmounted.
• Define closeNotification function to set the component is removed from DOM by displaying fading out animation and set isShown to false via setTimeout().
• Define the component, which renders the alert component with user defined message and a close button to remove the component from DOM.

代码实现

@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';
}

使用样例

function Notification(props) {
    const [isShown, setIsShown] = React.useState(false);
    const [isLeaving, setIsLeaving] = React.useState(false);

    let timeoutId = null;

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

    const closeNotification = () => {
      setIsLeaving(true);
      timeoutId = setTimeout(() => {
        setIsLeaving(false);
        setIsShown(false);
      }, 250)
    }

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

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