问题

以下是您要翻译的代码部分：

My working code before converting all my state into context:

**App.js**
```javascript
function App() {
  const [reptile, setReptile] = useState(function () {
    const storedValue = localStorage.getItem("reptiles");
    return JSON.parse(storedValue);
  })...

...useEffect(
    function () {
      localStorage.setItem("reptiles", JSON.stringify(reptile));
    },
    [reptile]
  );

My current code:

Context.js

const ReptileContext = createContext();

function ReptileProvider({ children }) {
  const [reptile, setReptile] = useState(function () {
    const storedValue = localStorage.getItem("reptiles");
    return JSON.parse(storedValue);
  });

  const [daysFed, setDaysFed] = useState("");
  const [displayForm, setDisplayForm] = useState(false);
  const [displayList, setDisplayList] = useState(true);
  const [displayReptile, setDisplayReptile] = useState(false);
  const [selectedReptile, setSelectedReptile] = useState(null);
  const [today, setToday] = useState(null);
  const [reptileType, setReptileType] = useState("");
  const [reptileName, setReptileName] = useState("");
  const [notes, setNotes] = useState("");

  function handleAddReptile(reptile) {
    setReptile((reptiles) => [...reptiles, reptile]);
  }

  function handleDeleteReptile(reptileId) {
    setReptile((reptiles) => reptiles.filter((rep) => rep.id !== reptileId));
  }

  function handleSelection(reptileId) {
    setSelectedReptile(reptileId);
    setDisplayList(false);
    setDisplayReptile(true);
  }

  function handleBack() {
    setDisplayReptile(false);
    setDisplayList(true);
  }

  return (
    <ReptileContext.Provider
      value={{
        reptile,
        reptileType,
        setReptileType,
        reptileName,
        setReptileName,
        notes,
        setNotes,
        daysFed,
        setDaysFed,
        displayForm,
        setDisplayForm,
        displayList,
        setDisplayList,
        displayReptile,
        setDisplayReptile,
        selectedReptile,
        setSelectedReptile,
        today,
        setToday,
        handleAddReptile,
        handleDeleteReptile,
        handleSelection,
        handleBack,
      }}
    >
      {children}
    </ReptileContext.Provider>
  );
}

function useReptile() {
  const context = useContext(ReptileContext);
  if (context === undefined)
    throw new Error("PostContext was used outside of the PostProvider");
  return context;
}

export { ReptileProvider, useReptile };

App.js

function App() {
  const { displayForm, displayList, displayReptile, selectedReptile, reptile } =
    useReptile();

  useEffect(
    function () {
      if (!reptile) return;
      localStorage.setItem("reptiles", JSON.stringify(reptile));
    },
    [reptile]
  );

index.js

<ReptileProvider>
      <App />
    </ReptileProvider>

I'm receiving an error upon load that reads "JSON.parse: unexpected character at line 1 column 1 of the JSON data". I believe the issue is directly related to where the useEffect hook is placed but I'm not entirely sure. Any help would be greatly appreciated, thanks!

<details>
<summary>英文:</summary>
My working code before converting all my state into context: 
**App.js**

function App() {
const [reptile, setReptile] = useState(function () {
const storedValue = localStorage.getItem("reptiles");
return JSON.parse(storedValue);
})...

...useEffect(
function () {
localStorage.setItem("reptiles", JSON.stringify(reptile));
},
[reptile]
);

My current code:
**Context.js**

const ReptileContext = createContext();

function ReptileProvider({ children }) {
const [reptile, setReptile] = useState(function () {
const storedValue = localStorage.getItem("reptiles");
return JSON.parse(storedValue);
});

const [daysFed, setDaysFed] = useState("");
const [displayForm, setDisplayForm] = useState(false);
const [displayList, setDisplayList] = useState(true);
const [displayReptile, setDisplayReptile] = useState(false);
const [selectedReptile, setSelectedReptile] = useState(null);
const [today, setToday] = useState(null);
const [reptileType, setReptileType] = useState("");
const [reptileName, setReptileName] = useState("");
const [notes, setNotes] = useState("");

function handleAddReptile(reptile) {
setReptile((reptiles) => [...reptiles, reptile]);
}

function handleDeleteReptile(reptileId) {
setReptile((reptiles) => reptiles.filter((rep) => rep.id !== reptileId));
}

function handleSelection(reptileId) {
setSelectedReptile(reptileId);
setDisplayList(false);
setDisplayReptile(true);
}

function handleBack() {
setDisplayReptile(false);
setDisplayList(true);
}

return (
<ReptileContext.Provider
value={
(reptile,
reptileType,
setReptileType,
reptileName,
setReptileName,
notes,
setNotes,
daysFed,
setDaysFed,
displayForm,
setDisplayForm,
displayList,
setDisplayList,
displayReptile,
setDisplayReptile,
selectedReptile,
setSelectedReptile,
today,
setToday,
handleAddReptile,
handleDeleteReptile,
handleSelection,
handleBack)
}
>
{children}
</ReptileContext.Provider>
);
}

function useReptile() {
const context = useContext(ReptileContext);
if (context === undefined)
throw new Error("PostContext was used outside of the PostProvider");
return context;
}

export { ReptileProvider, useReptile };

**App.js**

function App() {
const { displayForm, displayList, displayReptile, selectedReptile, reptile } =
useReptile();

useEffect(
function () {
if (!reptile) return;
localStorage.setItem("reptiles", JSON.stringify(reptile));
},
[reptile]
);

**index.js**

<ReptileProvider>
<App />
</ReptileProvider>

I'm receiving an error upon load that reads "JSON.parse: unexpected character at line 1 column 1 of the JSON data". I believe the issue is directly related to where the useEffect hook is placed but I'm not entirely sure. Any help would be greatly appreciated, thanks!
</details>
# 答案1
**得分**: 2
我认为问题不在于`useEffect`钩子，而在于您将值传递给`ReptileContext.Provider`的方式。您使用的是括号而不是花括号，这意味着您传递的是单个表达式而不是对象。这可能会导致在尝试读取存储的值时`JSON.parse`失败。
```jsx
<ReptileContext.Provider value={{ ... }}></ReptileContext.Provider>

<ReptileContext.Provider value={{ ... }}></ReptileContext.Provider>