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带有React Hooks useCallback的简单示例的麻烦

我正在尝试制作一个简单的示例,该示例遵循文档https://reactjs.org/docs/hooks-reference.html#usecallback上文档中的React Hooks示例

如果没有useCallback代码,请按以下示例进行查找:

import React, { useCallback } from "react";

function Test(props) {
  function doSomething(a, b) {
    console.log("doSomething called");
    return a + b;
  }

  return (
    <div>
      {Array.from({ length: 3 }).map(() => (
        <div>{doSomething('aaa','bbb')}</div>
      ))}
    </div>
  );
}

export default Test;
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但是,当我添加我认为正确的代码useCallback如下时,出现错误(未定义a)

import React, { useCallback } from "react";

function Test(props) {
  function doSomething(a, b) {
    console.log("doSomething called");
    return a + b;
  }

  const memoizedCallback = useCallback(
    () => {
      doSomething(a, b);
    },
    [a, …
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