精读《怎么用 React Hooks 造轮子》

useDocumentTitle("个人中心");

function useDocumentTitle(title) {
  useEffect(
    () => {
      document.title = title;
      return () => (document.title = "前端精读");
    },
    [title]
  );
}

const windowSize = useWindowSize();
return <div>页面高度：{windowSize.innerWidth}</div>;

function getSize() {
  return {
    innerHeight: window.innerHeight,
    innerWidth: window.innerWidth,
    outerHeight: window.outerHeight,
    outerWidth: window.outerWidth
  };
}

function useWindowSize() {
  let [windowSize, setWindowSize] = useState(getSize());

  function handleResize() {
    setWindowSize(getSize());
  }

  useEffect(() => {
    window.addEventListener("resize", handleResize);
    return () => {
      window.removeEventListener("resize", handleResize);
    };
  }, []);

  return windowSize;
}

const className = useCss({
  color: "red"
});

return <div className={className}>Text.</div>;

const ref = useRef(null);
let componentSize = useComponentSize(ref);

return (
  <>
    {componentSize.width}
    <textArea ref={ref} />
  </>
);

useLayoutEffect(() => {
  handleResize();

  let resizeObserver = new ResizeObserver(() => handleResize());
  resizeObserver.observe(ref.current);

  return () => {
    resizeObserver.disconnect(ref.current);
    resizeObserver = null;
  };
}, []);

let name = useInputValue("Jamie");
// name = { value: 'Jamie', onChange: [Function] }
return <input {...name} />;

function useInputValue(initialValue) {
  let [value, setValue] = useState(initialValue);
  let onChange = useCallback(function(event) {
    setValue(event.currentTarget.value);
  }, []);

  return {
    value,
    onChange
  };
}

const value = useRaf(1000);

const [target, setTarget] = useState(50);
const value = useSpring(target);

return <div onClick={() => setTarget(100)}>{value}</div>;

useEffect(
  () => {
    if (spring) {
      spring.setEndValue(targetValue);
    }
  },
  [targetValue]
);

const value = useTween();

const fn: Easing = easing[easingName];
const t = useRaf(ms, delay);

return fn(t);

const { loading, error, result } = useAsync(fetchUser, [id]);

export function useAsync(asyncFunction) {
  const asyncState = useAsyncState(options);

  useEffect(() => {
    const promise = asyncFunction();
    asyncState.setLoading();
    promise.then(
      result => asyncState.setResult(result);,
      error => asyncState.setError(error);
    );
  }, params);
}

async componentDidMount() {
  // setState: 改 isLoading state
  try {
    const data = await fetchUser()
    // setState: 改 isLoading、error、data
  } catch (error) {
    // setState: 改 isLoading、error
  }
}

@Connect(...)
class App extends React.PureComponent {
  public componentDidMount() {
    this.props.fetchUser()
  }

  public render() {
    // this.props.userData.isLoading | error | data
  }
}

function App() {
  const { isLoading, error, data } = useFetchUser();
}

const fetchUser = id =>
  fetch(`xxx`).then(result => {
    if (result.status !== 200) {
      throw new Error("bad status = " + result.status);
    }
    return result.json();
  });

function useFetchUser(id) {
  const asyncFetchUser = useAsync(fetchUser, id);
  return asyncUser;
}

function App() {
  const { getFieldDecorator } = useAntdForm();

  return (
    <Form onSubmit={this.handleSubmit} className="login-form">
      <FormItem>
        {getFieldDecorator("userName", {
          rules: [{ required: true, message: "Please input your username!" }]
        })(
          <Input
            prefix={<Icon type="user" style={{ color: "rgba(0,0,0,.25)" }} />}
            placeholder="Username"
          />
        )}
      </FormItem>
      <FormItem>
        <Button type="primary" htmlType="submit" className="login-form-button">
          Log in
        </Button>
        Or <a href="">register now!</a>
      </FormItem>
    </Form>
  );
}

const [formState, { text, password }] = useFormState();
return (
  <form>
    <input {...text("username")} required />
    <input {...password("password")} required minLength={8} />
  </form>
);

export function useFormState(initialState) {
  const [state, setState] = useReducer(stateReducer, initialState || {});

  const createPropsGetter = type => (name, ownValue) => {
    const hasOwnValue = !!ownValue;
    const hasValueInState = state[name] !== undefined;

    function setInitialValue() {
      let value = "";
      setState({ [name]: value });
    }

    const inputProps = {
      name, // 给 input 添加 type: text or password
      get value() {
        if (!hasValueInState) {
          setInitialValue(); // 给初始化值
        }
        return hasValueInState ? state[name] : ""; // 赋值
      },
      onChange(e) {
        let { value } = e.target;
        setState({ [name]: value }); // 修改对应 Key 的值
      }
    };

    return inputProps;
  };

  const inputPropsCreators = ["text", "password"].reduce(
    (methods, type) => ({ ...methods, [type]: createPropsGetter(type) }),
    {}
  );

  return [
    { values: state }, // formState
    inputPropsCreators
  ];
}

useMount(() => {
  // quite similar to `componentDidMount`
});

useEffect(() => void fn(), []);

useUnmount(() => {
  // quite similar to `componentWillUnmount`
});

useEffect(() => fn, []);

useUpdate(() => {
  // quite similar to `componentDidUpdate`
});

const mounting = useRef(true);
useEffect(() => {
  if (mounting.current) {
    mounting.current = false;
  } else {
    fn();
  }
});

const update = useUpdate();

const useUpdate = () => useState(0)[1];

const isMounted = useIsMounted();

const [isMount, setIsMount] = useState(false);
useEffect(() => {
  if (!isMount) {
    setIsMount(true);
  }
  return () => setIsMount(false);
}, []);
return isMount;

const store = createStore({
  user: {
    name: "小明",
    setName: (state, payload) => {
      state.name = payload;
    }
  }
});

const App = () => (
  <StoreProvider store={store}>
    <YourApp />
  </StoreProvider>
);

function YourApp() {
  const userName = useStore(state => state.user.name);
  const setName = userAction(dispatch => dispatch.user.setName);
}

const StoreContext = createContext();

const StoreProvider = ({ children, store }) => (
  <StoreContext.Provider value={store}>{children}</StoreContext.Provider>
);

const store = useContext(StoreContext);
return store;

import { Toggle } from 'react-powerplug'

function App() {
  return (
    <Toggle initial={true}>
      {({ on, toggle }) => (
        <Checkbox checked={on} onChange={toggle} />
      )}
    </Toggle>
  )
}
↓ ↓ ↓ ↓ ↓ ↓
import { useToggle } from 'react-powerhooks'

function App() {
  const [on, toggle] = useToggle()
  return <Checkbox checked={on} onChange={toggle} />
}

export function Toggle() {
  // 这是 Toggle 的源码
  // balabalabala..
}

const App = wrap(() => {
  // 第一步：包 wrap
  const [on, toggle] = useRenderProps(Toggle); // 第二步：包 useRenderProps
});

const wrappers = []; // 全局存储 wrappers

export const useRenderProps = (WrapperComponent, wrapperProps) => {
  const [args, setArgs] = useState([]);
  const ref = useRef({});
  if (!ref.current.initialized) {
    wrappers.push({
      WrapperComponent,
      wrapperProps,
      setArgs
    });
  }
  useEffect(() => {
    ref.current.initialized = true;
  }, []);
  return args; // 通过下面 wrap 调用 setArgs 获取值。
};

export const wrap = FunctionComponent => props => {
  const element = FunctionComponent(props);
  const ref = useRef({ wrapper: wrappers.pop() }); // 拿到 useRenderProps 提供的 Toggle
  const { WrapperComponent, wrapperProps } = ref.current.wrapper;
  return createElement(WrapperComponent, wrapperProps, (...args) => {
    // WrapperComponent => Toggle，这一步是在构造 RenderProps 执行环境
    if (!ref.current.processed) {
      ref.current.wrapper.setArgs(args); // 拿到 on、toggle 后，通过 setArgs 传给上面的 args。
      ref.current.processed = true;
    } else {
      ref.current.processed = false;
    }
    return element;
  });
};

const useToggle = initialValue => {
  const [on, setOn] = useState(initialValue);
  return {
    on,
    toggle: () => setOn(!on)
  };
};

const Toggle = ({ initialValue, children, render = children }) =>
  renderProps(render, useToggle(initialValue));

const nextState = produce(baseState, draftState => {
  draftState.push({ todo: "Tweet about it" });
  draftState[1].done = true;
});

function useImmer(initialValue) {
  const [val, updateValue] = React.useState(initialValue);
  return [
    val,
    updater => {
      updateValue(produce(updater));
    }
  ];
}

const [value, setValue] = useImmer({ a: 1 });

value(obj => (obj.a = 2)); // immutable