Lodash debounce TypeError: Expected a function react

Question

我正在尝试使用 debounce 函数来避免在数据表中键入和搜索内容时进行多次调用。我现在做的是在input

onChange={(e) => {
            const delayedQuery = useCallback(debounce(this.handleSearch(e.target.value), 500));
            return delayedQuery
          }}

其中 handeSearch 是

handleSearch(filter) {
      service.getData(filter).subscribe((data) => {console.log(data)})
    }

但我有这个错误 TypeError: Expected a function。该服务正在运行，但没有去抖动。它在我打字的同时一个字符一个字符地写入，这是不正确的。

Answer 1

你不能在 class 组件或事件处理函数中使用钩子，你必须将函数传递给 lodash debounce。

还有；如果您尝试从事件中异步读取 target.value，您将收到 this synthetic event is reused for performance reasons 错误。

在聊天中我假设你使用 rxjs from(promise) 所以你仍然有一个问题，当用户输入并且你触发异步请求时，他们可能会以不同的顺序解析。

查看下面的错误示例（快速输入 hai 并等待 2 秒，它解析为 ha）

//simple debounce implementation
const debounce = (fn, delay = 50) => {
  let time;
  return (...args) => {
    clearTimeout(time);
    time = setTimeout(() => fn(...args), delay);
  };
};
//service where you can subscribe to
const service = (() => {
  let listeners = [];
  const later = (value, time = 50) =>
    new Promise((r) =>
      //if search is 2 characters long it'll resolve much later
      setTimeout(
        () => r(value),
        value.length === 2 ? 2000 : time
      )
    );
  //subscribe returns an unsubscribe function
  const subScribe = (fn) => {
    listeners.push(fn);
    //return the Subscriber object
    //https://rxjs-dev.firebaseapp.com/api/index/class/Subscriber
    return {
      unsubscribe: () =>
        (listeners = listeners.filter(
          (listener) => listener !== fn
        )),
    };
  };
  //notify all listeners
  const notify = (value) =>
    listeners.forEach((listener) => listener(value));
  return {
    getData: (value) => ({
      subScribe: (fn) => {
        const unsub = subScribe(fn);
        later(value).then((value) => notify(value));
        return unsub;
      },
    }),
  };
})();

class App extends React.PureComponent {
  constructor(props) {
    super(props);
    this.state = { asyncSearchResult: '' };
    //use handleSearch to create a debounced version of it
    this.handleSearchDebounced = debounce(
      this.handleSearch
    ).bind(this); //you need to bind it to guearantee correct context
  }
  rendered = 0;
  handleSearch = (value) =>
    service
      .getData(value)
      .subScribe((value) =>
        this.setState({ asyncSearchResult: value })
      );
  render() {
    return (
      <div>
        <input
          type="text"
          // pass value to the handler, not the event
          onChange={(e) =>
            this.handleSearchDebounced(e.target.value)
          }
        />
        async result: {this.state.asyncSearchResult}
      </div>
    );
  }
}
ReactDOM.render(<App />, document.getElementById('root'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>

解决方法如下：

//simple debounce implementation
const debounce = (fn, delay = 50) => {
  let time;
  return (...args) => {
    clearTimeout(time);
    time = setTimeout(() => fn(...args), delay);
  };
};
//service where you can subscribe to
const service = (() => {
  let listeners = [];
  const later = (value, time = 50) =>
    new Promise((r) =>
      //if search is 2 characters long it'll resolve much later
      setTimeout(
        () => r(value),
        value.length === 2 ? 2000 : time
      )
    );
  //subscribe returns an unsubscribe function
  const subScribe = (fn) => {
    listeners.push(fn);
    //return the Subscriber object
    //https://rxjs-dev.firebaseapp.com/api/index/class/Subscriber
    return {
      unsubscribe: () =>
        (listeners = listeners.filter(
          (listener) => listener !== fn
        )),
    };
  };
  //notify all listeners
  const notify = (value) =>
    listeners.forEach((listener) => listener(value));
  return {
    getData: (value) => ({
      subScribe: (fn) => {
        const unsub = subScribe(fn);
        later(value).then((value) => notify(value));
        return unsub;
      },
    }),
  };
})();
const latestGetData = (value) => {
  const shared = {};
  return {
    subScribe: (fn) => {
      const current = {};
      shared.current = current;
      const subscriber = service
        .getData(value)
        .subScribe((result) => {
          //only call subscriber of latest resolved
          if (shared.current === current) {
            fn(result);
          }
          subscriber.unsubscribe();
        });
    },
  };
};
class App extends React.PureComponent {
  constructor(props) {
    super(props);
    this.state = { asyncSearchResult: '' };
    //use handleSearch to create a debounced version of it
    this.handleSearchDebounced = debounce(
      this.handleSearch
    ).bind(this); //you need to bind it to guearantee correct context
  }
  rendered = 0;
  handleSearch = (value) =>
    latestGetData(value).subScribe((value) =>
      this.setState({ asyncSearchResult: value })
    );
  render() {
    return (
      <div>
        <input
          type="text"
          // pass value to the handler, not the event
          onChange={(e) =>
            this.handleSearchDebounced(e.target.value)
          }
        />
        async result: {this.state.asyncSearchResult}
      </div>
    );
  }
}
ReactDOM.render(<App />, document.getElementById('root'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>

Lodash debounce TypeError: Expected a function react

Lodash debounce TypeError: Expected a function react

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