Question

我正在尝试创建一个我正在使用React钩子的React应用程序。在登录表单中，当用户提交表单时，电子邮件和密码将传递给handleClick函数。该函数从服务器获取数据并显示在客户端，但是响应始终是未定义的，并且在从服务返回之前被调用。这是代码...

Login.js

import React, { useState, useEffect } from 'react';
import { Button, Form, Container, Row, Col } from 'react-bootstrap';
import './login.css'
import * as services from '../services'

function Login() {

    const [email, setEmail] = useState('');
    const [password, setPassword] = useState('');

    const handleClick = async(e) => {
        e.preventDefault();
        console.log(email, password);
        let res = await services.login(email, password);
        console.log(res);
    }    

    return (
        <Container>
            <Row className="justify-content-md-center ">
                <header><h2>Rao infotech workspace</h2></header>
            </Row>
            <Row className="justify-content-md-center form">
                <Col md="auto">
                    <Form onSubmit={handleClick}>
                        <Form.Group controlId="formBasicEmail">
                            <Form.Label>Email address</Form.Label>
                            <Form.Control type="email" placeholder="Enter email" onChange={(e) => setEmail(e.target.value)} />
                        </Form.Group>

                        <Form.Group controlId="formBasicPassword">
                            <Form.Label>Password</Form.Label>
                            <Form.Control type="password" placeholder="Password" onChange={(e) => setPassword(e.target.value)} />
                        </Form.Group>
                        <Button variant="primary" type="submit" >
                            Submit
            </Button>
                    </Form>
                </Col>

            </Row>
        </Container>
    );


}

export default Login;

services.js

import axios from "axios";
const baseUrl = "http://localhost:4000/"; 

export function login(email, password) {
    var body = {email: email, password: password}
    axios.post(baseUrl + 'user/login', body)
    .then((res)=>{
        console.log("res in service", res);
        return res;
    })
}

我尝试使用useEffect，但无法在useEffect（）中调用函数

Answer 1

您需要返回login函数：

export async function login(email, password) {
    var body = {email: email, password: password}
    return axios.post(baseUrl + 'user/login', body)
    .then((res)=>{
        console.log("res in service", res);
        return res;
    })
}

或者简单地：

export async function login(email, password) {
    var body = {email: email, password: password}
    return axios.post(baseUrl + 'user/login', body);
}

Answer 2

import axios from "axios";
const baseUrl = "http://localhost:4000/"; 

export function login(email, password) {
 var body = {email: email, password: password}
 return new Promise((resolve, reject) => {
   axios.post(baseUrl + 'user/login', body)
  .then((res)=>{
    console.log("res in service", res);
    return resolve(res);
    });
  })
}

只需在服务中创建承诺，异步/等待将开始工作。

Answer 3

您的service.js登录功能未返回承诺，因此您无法等待其结果

异步/等待不与React JS一起工作（hooks）

3 个答案: