在react 16中，我使用

<Input id="number" 
       type="time" 
       onChange={(evt) => { console.log(evt.target.value); }} />

通过这样做来获得输入字段值:

import React, { Component } from 'react';

class App extends Component {

constructor(props){
super(props);

this.state = {
  username : ''
}

this.updateInput = this.updateInput.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}


updateInput(event){
this.setState({username : event.target.value})
}


handleSubmit(){
console.log('Your input value is: ' + this.state.username)
//Send state to the server code
}



render(){
return (
    <div>
    <input type="text" onChange={this.updateInput}></input>
    <input type="submit" onClick={this.handleSubmit} ></input>
    </div>
  );
}
} 

//output
//Your input value is: x

在功能组件中:-

export default function App(){

const [state, setState] = useState({
        value:'',
        show:''
    });

const handleChange = (e) => {
    setState({value: e.target.value})
}

const submit = () => {
    setState({show: state.value})
}

return(
        <>
            <form onSubmit={()=>submit()}>
                <input type="text" value={state.value} onChange={(e)=>handleChange(e)} />
                <input type="submit" />
            </form>
            <h2>{state.show}</h2>
        </>
)}

export default class MyComponent extends React.Component {

onSubmit(e) {
    e.preventDefault();
    var title = this.title.value; //added .value
    console.log(title);
}

render(){
    return (
        ...
        <form className="form-horizontal">
            ...
            <input type="text" className="form-control" ref={input => this.title = input} name="title" />
            ...
        </form>
        ...
        <button type="button" onClick={this.onSubmit} className="btn">Save</button>
        ...
    );
}

};

使用不受控字段:

export default class MyComponent extends React.Component {

    onSubmit(e) {
        e.preventDefault();
        console.log(e.target.neededField.value);
    }

    render(){
        return (
            ...
            <form onSubmit={this.onSubmit} className="form-horizontal">
                ...
                <input type="text" name="neededField" className="form-control" ref={(c) => this.title = c}/>
                ...
            </form>
            ...
            <button type="button" className="btn">Save</button>
            ...
        );
    }

};

你的错误是因为你使用类，当使用类时，我们需要绑定函数与此，以便工作得很好。不管怎么说，有很多教程告诉我们为什么要用“this”，以及“this”在javascript中是做什么的。

如果你修正了提交按钮，它应该是工作的:

<button type="button" onClick={this.onSubmit.bind(this)} className="btn">Save</button>

如果你想在控制台显示输入值你应该使用var title = this。title。value;