从react中导入{useState}

导出默认函数App() { const [data, setData] = useState({})

const updateData = e => {
    setData({
        ...data,
        [e.target.name]: e.target.value
    })
}

const submit = e => {
    e.preventDefault()
    console.log(data)
}

return (
    <form onSubmit={submit}>
        <input
            name="email"
            type="email"
            onChange={updateData}
        />
        <input
            name="password"
            type="password"
            onChange={updateData}
         />
        <button>Submit</button>
    </form>
)

}

使用输入中的change事件来更新组件的状态，并在handllogin中访问它:

handleEmailChange: function(e) {
   this.setState({email: e.target.value});
},
handlePasswordChange: function(e) {
   this.setState({password: e.target.value});
},
render : function() {
      return (
        <form>
          <input type="text" name="email" placeholder="Email" value={this.state.email} onChange={this.handleEmailChange} />
          <input type="password" name="password" placeholder="Password" value={this.state.password} onChange={this.handlePasswordChange}/>
          <button type="button" onClick={this.handleLogin}>Login</button>
        </form>);
},
handleLogin: function() {
    console.log("EMail: " + this.state.email);
    console.log("Password: " + this.state.password);
}

工作小提琴。

此外，阅读文档，有一个完整的部分专门用于表单处理:表单

以前你也可以使用React的双向数据绑定助手mixin来实现同样的事情，但现在它被弃用了，取而代之的是设置值和更改处理程序(如上所述):

var ExampleForm = React.createClass({
  mixins: [React.addons.LinkedStateMixin],
  getInitialState: function() {
    return {email: '', password: ''};
  },
  handleLogin: function() {
    console.log("EMail: " + this.state.email);
    console.log("Password: " + this.state.password);
  },
  render: function() {
    return (
      <form>
        <input type="text" valueLink={this.linkState('email')} />
        <input type="password" valueLink={this.linkState('password')} />
        <button type="button" onClick={this.handleLogin}>Login</button>
      </form>
    );
  }
});

文档在这里:双向绑定助手。

对于typescript用户

import react from 'react'

interface FormInterface {
    [key: string]: string
}

const handleSubmit = (event: React.FormEvent<HTMLFormElement>) => {
   event.preventDefault();
   let formData = new FormData(event.currentTarget)
   let formObj: FormInterface = {}
   for (let [key, value] of Array.from(formData.entries())) {
     formObj[key] = value.toString()
   }
};

<form onSubmit={handleSubmit}>
   <input type="text" name="email" placeholder="Email" />
   <input type="password" name="password" placeholder="Password" />
   <button type="submit">Login</button>
</form>

同样，这个也可以用。

handleChange: function(state,e) {
  this.setState({[state]: e.target.value});
},
render : function() {
  return (
    <form>
      <input type="text" name="email" placeholder="Email" value={this.state.email} onChange={this.handleChange.bind(this, 'email')} />
      <input type="password" name="password" placeholder="Password" value={this.state.password} onChange={this.handleChange.bind(this, 'password')}/>
      <button type="button" onClick={this.handleLogin}>Login</button>
    </form>
  );
},
handleLogin: function() {
  console.log("EMail: ", this.state.email);
  console.log("Password: ", this.state.password);
}

另一种方法是使用ref属性并使用this.refs引用值。这里有一个简单的例子:

render: function() {
    return (<form onSubmit={this.submitForm}>
        <input ref="theInput" />
    </form>);
},
submitForm: function(e) {
    e.preventDefault();
    alert(React.findDOMNode(this.refs.theInput).value);
}

更多信息可以在React文档中找到: https://facebook.github.io/react/docs/more-about-refs.html#the-ref-string-attribute

关于如何在React中使用单选按钮中描述的很多原因?这种方法并不总是最好的，但在一些简单的情况下确实是一种有用的替代方法。

对于那些不想使用ref和OnChange事件重置状态的人，你可以只使用简单的OnSubmit句柄和循环FormData对象。

注意，你不能直接访问formData.entries()，因为它是一个可迭代对象，你必须循环遍历它。

这个例子使用了React Hooks:

const LoginPage = () => {
  const handleSubmit = (event) => {
    const formData = new FormData(event.currentTarget);
    event.preventDefault();
    for (let [key, value] of formData.entries()) {
      console.log(key, value);
    }
  };

  return (
    <div>
      <form onSubmit={handleSubmit}>
        <input type="text" name="username" placeholder="Email" />
        <input type="password" name="password" placeholder="Password" />
        <button type="submit">Login</button>
      </form>
    </div>
  );
};

如果你使用的是TypeScript:

export const LoginPage: React.FC<{}> = () => {
  const handleSubmit: React.FormEventHandler<HTMLFormElement> = (event) => {
    const formData = new FormData(event.currentTarget);
    event.preventDefault();
    for (let [key, value] of formData.entries()) {
      console.log(key, value);
    }
  };

  return (
    <div>
      <form onSubmit={handleSubmit}>
        <input type="text" name="username" placeholder="Email" />
        <input type="password" name="password" placeholder="Password" />
        <button type="submit">Login</button>
      </form>
    </div>
  );
};