问从数组中获取对象值

EN

   myArr = [[{a: 1, b: 2}], [{a: 1, b:2}], [{a: 1, b:2}]]
   // I want to extract only the values of b and make them into array 
   // my asnwer should look like this: 
   // [2,2,2]

  const [answerArr, setAnswerArr] = useState([]);
  useEffect(() => {
    const extractCode = () => {
      const res = myArr.map((item)=>{
          ????
       })
    };
    extractCode();
  }, [codeArr]);