模块构建失败(from ./node_modules/babel-loader/lib/index.js)

Question

我有这个代码在我的App.js:

import React, {useEffect, useState} from 'react'
function App() {
const [backendData, setBackendData] = useState([{}])
useEffect(() => {
fetch("/api").then(response => response.json()).then(
data => {
setBackendData(data)
}
)
}, [])
return (
<div>
{(typeof backendData.users === 'undefined') ? (
<p>Loading...</p>
): (
backendData.users.map(user, i) => (
<p key={i}>
{user}
</p>
))

)}
</div>
)
}
export default App

，我一直收到这个错误:

./src/App.js

模块构建失败(from ./node_modules/babel-loader/lib/index.js):SyntaxError: E:InterconnectclientsrcApp.js: Unexpected token, expected ";(19:39)

第19行是这样的:

backendData.users.map(user, i) => (

Answer 1

正确的语法是

backendData.users.map((user, i) => (
<p key={i}>
{user}
</p>
))

用一对圆括号括住(user, i) => (...)函数。