hooks in react

import React, { useState, useEffect } from "react";
export default props => {
  console.log("componentWillMount");
  console.log("componentWillReceiveProps", props);
  const [x, setX] = useState(0);
  const [y, setY] = useState(0);
  const [moveCount, setMoveCount] = useState(0);
  const [cross, setCross] = useState(0);
  const mouseMoveHandler = event => {
    setX(event.clientX);
    setY(event.clientY);
  };
  useEffect(() => {
    console.log("componentDidMount");
    document.addEventListener("mousemove", mouseMoveHandler);
    return () => {
      console.log("componentWillUnmount");
      document.removeEventListener("mousemove", mouseMoveHandler);
    };
  }, []); // empty-array means don't watch for any updates
  useEffect(
    () => {
      // if (componentDidUpdate & (x or y changed))
      setMoveCount(moveCount + 1);
    },
    [x, y]
  );
useEffect(() => {
    // if componentDidUpdate or componentDidMount
    if (x === y) {
      setCross(x);
    }
  });
  return (
    <div>
      <p style={{ color: props.color }}>
        Your mouse is at {x}, {y} position.
      </p>
      <p>Your mouse has moved {moveCount} times</p>
      <p>
        X and Y positions were last equal at {cross}, {cross}
      </p>
    </div>
  );
};

View another examples Add Own solution

Taher Wala 85 points

                                    function ExampleWithManyStates() {
  // Declare multiple state variables!
  const [age, setAge] = useState(42);
  const [fruit, setFruit] = useState('banana');
  const [todos, setTodos] = useState([{ text: 'Learn Hooks' }]);
  // ...
}

Thank you! 2

4.13

ShrunkenHeads 120 points

                                    import React, { useState } from 'react';
function Example() {
  // Declare a new state variable, which we'll call &quot;count&quot;  const [count, setCount] = useState(0);
  return (
    &lt;div&gt;
      &lt;p&gt;You clicked {count} times&lt;/p&gt;
      &lt;button onClick={() =&gt; setCount(count + 1)}&gt;
        Click me
      &lt;/button&gt;
    &lt;/div&gt;
  );
}

Thank you! 8

4.13 (8 Votes)

3.25

Shelby I. 85 points

                                    import React, { useState } from 'react';

function Example() {
  // Declare a new state variable, which we'll call &quot;count&quot;  const [count, setCount] = useState(0);
  return (
    &lt;div&gt;
      &lt;p&gt;You clicked {count} times&lt;/p&gt;
      &lt;button onClick={() =&gt; setCount(count + 1)}&gt;
        Click me
      &lt;/button&gt;
    &lt;/div&gt;
  );
}

Thank you! 4

3.25 (4 Votes)

Lucas Labruyere 85 points

                                    import React, { useState, useEffect } from 'react';

function FriendStatus(props) {
  const [isOnline, setIsOnline] = useState(null);  useEffect(() =&gt; {    function handleStatusChange(status) {      setIsOnline(status.isOnline);    }    ChatAPI.subscribeToFriendStatus(props.friend.id, handleStatusChange);    return () =&gt; {      ChatAPI.unsubscribeFromFriendStatus(props.friend.id, handleStatusChange);    };  });
  if (isOnline === null) {
    return 'Loading...';
  }
  return isOnline ? 'Online' : 'Offline';
}

Thank you! 7

3.4

Blisterinthesun 115 points

                                    const [state, setState] = useState(initialState);

Thank you! 5

3.4 (5 Votes)

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