分配或函数调用React.js

Question

以下代码存在错误。

我必须在JavaScript中加载对象并在JavaScript中创建模型。为此，我使用下面的代码。执行包含的代码后，l将在下面显示错误。

错误：

  

期望分配或函数调用，而看到一个表达式no-unused-expressions

代码：

import * as React from 'react';
import { Button, Form, FormGroup, FormControl, ControlLabel } from "react-bootstrap";
import logo from './logo.svg';
import { HeadProvider, Title, Link, Meta } from 'react-head';
import * as Router from 'react-router';
import './Home.css';
import RegisterPage from "./Register.js"; //L'oggetto RegisterPage contiene l'oggetto Register

<Router.Route path="./Register.js" component={RegisterPage.Register} />

class Home extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      email: "",
      password: ""
    };
  }

  validateForm() {
    return this.state.email.length > 0 && this.state.password.length > 0;
  }
  handleChange = event => {
    this.setState({
      [event.target.id]: event.target.value
    });
  }

  handleSubmit = event => {
    event.preventDefault();
  }

  render() {
    return (
        <React.Fragment>
            <HeadProvider>
                <Meta charset="UTF-8"/>
                <Meta name="viewport" content="width=device-width, initial-scale=1"/>
                <Link rel="icon" type="image/png" href="images/icons/favicon.ico"/>
                <Link rel="stylesheet" type="text/css"
                      href="vendor/bootstrap/css/bootstrap.min.css"/>
                <Link rel="stylesheet" type="text/css"
                      href="fonts/font-awesome-4.7.0/css/font-awesome.min.css"/>
                <Link rel="stylesheet" type="text/css"
                      href="fonts/iconic/css/material-design-iconic-font.min.css"/>
                <Link rel="stylesheet" type="text/css" href="vendor/animate/animate.css"/>
                <Link rel="stylesheet" type="text/css"
                      href="vendor/css-hamburgers/hamburgers.min.css"/>
                <Link rel="stylesheet" type="text/css"
                      href="vendor/animsition/css/animsition.min.css"/>
                <Link rel="stylesheet" type="text/css" href="vendor/select2/select2.min.css"/>
                <Link rel="stylesheet" type="text/css"
                      href="vendor/daterangepicker/daterangepicker.css"/>
                <Link rel="stylesheet" type="text/css" href="css/util.css"/>
                <Link rel="stylesheet" type="text/css" href="css/main.css"/>
            </HeadProvider>
            <div className="Login">

                <Form onSubmit={this.handleSubmit}>
                    <Form.Group controlId="email" bsSize="large">
                        <label> Email: </label>
                        <Form.Control
                            autoFocus
                            type="email"
                            value={this.state.email}
                            onChange={this.handleChange}
                        />

                    </Form.Group>
                    <br></br>
                    <Form.Group controlId="password" bsSize="large">
                        <label> Password: </label>
                        <Form.Control
                            value={this.state.password}
                            onChange={this.handleChange}
                            type="password"
                        />
                    </Form.Group>
                    <Button
                        block
                        bsSize="large"
                        disabled={!this.validateForm()}
                        type="submit"
                    >
                        Login
                    </Button>
                </Form>
            </div>
        </React.Fragment>
    );
  }
}

export default Home;