Javascript TypeError:无法读取属性';名称';未定义的反应错误
每次我尝试在输入字段中键入内容时,我都无法在代码中找到解决此错误的方法。TypeError:无法读取未定义的属性“name” 我是新来的,对反应不太了解 这是我文件中的所有代码Javascript TypeError:无法读取属性';名称';未定义的反应错误,javascript,reactjs,Javascript,Reactjs,每次我尝试在输入字段中键入内容时,我都无法在代码中找到解决此错误的方法。TypeError:无法读取未定义的属性“name” 我是新来的,对反应不太了解 这是我文件中的所有代码 import React from'react'; import Notelist from '../componenets/notelist'; import { Link } from 'react-router-dom'; export default class NewPage extends React.Co
import React from'react';
import Notelist from '../componenets/notelist';
import { Link } from 'react-router-dom';
export default class NewPage extends React.Component {
state = {
note:{
title: '',
body: '',
createdAt: undefined,
updatedAt: undefined
}
}
updateValue = (e) => {
const { note } = this.state;
this.setState({
note: { ...note, [e.title.name]: e.target.value }
});
}
handleSave = (e) => {
e.preventDefault();
const id = this.props.onSave(this.state.note);
this.props.history.replace(`/notes/${ id }`);
}
render() {
const { note } = this.state;
return (
<div className="note-form">
<h1>New Note</h1>
<form onSubmit={this.handleSave}>
<div className="note-form-field">
<label>Title: </label><br/>
<input className="input-txt" type="text" name="title" value={note.title} onChange={this.updateValue}/>
</div>
<div className="note-form-field note-form-field-text">
<br/>
<textarea name="body" value={note.body} onChange={this.updateValue} />
</div>
<div className="note-form-buttons">
<button className="btn">Save</button>
<Link to="/">Cancel</Link>
</div>
</form>
</div>
);
}
}
查看编译的我相信您正在尝试将
标题
指定为键,将输入字段的值指定为值。你为什么不试试这个
updateValue = (e) => {
const { note } = this.state;
this.setState({
note: { ...note, "title": e.target.value }
});
}
updateValue方法中的参数e是事件对象,它将没有名为title.name的属性。如果要将title文本框的值存储到note对象的属性title中 所以你的代码可以是这样的
this.setState({
note: { ...note, title: e.target.value }
});
事件
对象(e)没有名为标题
的键,这就是为什么会出现“无法读取未定义的属性名”
您需要event.target
,它是指导致此事件发生的元素
尝试以下操作以动态更新状态值
。它将找到一个与元素的名称
匹配的键,并为其提供该元素的值(如用户输入):
从“React”导入React,{Component} 导出类Todolist2扩展组件{
state={name:'',items:'',price:'',arr:[],errors:{name:'',items:'',price:''}}
todoSubmit=(event)=>
{
event.preventDefault()
let list=this.state.arr;
let tododata={name:this.state.name, items:this.state.items, price:this.state.price};
list.push(tododata);
this.setState({arr:list});
console.log(this.state.arr);
}
handle=(event)=>
{
const {name,value}=event.target;
let errors=this.state.error;
switch(errors)
{
case 'name':errors.name=value.length<2?"Name must be 2 character long":'';
case 'items':errors.items=value.length<2?"items must be 2 character long":'';
case 'price':errors.price=value.length<2?"price must be 2 character long":'';
}
this.setState({errors,[name]:value})
this.setState({[name]:value})
console.log(this.state);
}
deldata=(ind)=>
{
if (window.confirm('Do u want to delete'))
{
let list=this.state.arr;
list.splice(ind,1);
this.setState({arr:list});
}
// alert('do u want to delete');
}
render() {
const {errors}=this.state;
return (
<div>
<h1>ToDo List 2</h1>
<form className='container' onSubmit={this.todoSubmit}>
<div className="form-group col-md-4">
<label>Name:</label>
<input type="text" name="name" className='form-control' onChange={this.handle}/>
{errors.name.length>0 && <span className='alert alert-danger'>{errors.name}</span> }
</div>
<div className="form-group col-md-4" onChange={this.handle}>
<label>Items:</label>
<input type="text" name="items" class='form-control'/>
{errors.items.length>0 && <span className='alert alert-danger'>{errors.items}</span> }
</div>
<div className="form-group col-md-4" onChange={this.handle}>
<label>Price:</label>
<input type="text" name="price" class='form-control'/>
{errors.price.length>0 && <span className='alert alert-danger'>{errors.price}</span> }
</div>
<input type='Submit' value='Submit' class='btn btn-outline-success' />
<table class='table'>
<tr>
<th>S.no</th>
<th>Name</th>
<th>Items</th>
<th>Price</th>
<th>Action</th>
</tr>
{this.state.arr.map((data,ind)=>
<tr>
<td>{ind+1}</td>
<td>{data.name}</td>
<td>{data.items}</td>
<td>{data.price}</td>
<td><button class="btn btn-info btn-lg " onClick={()=>this.deldata(ind)}>delete </button></td>
</tr>
)}
</table>
</form>
</div>
)
}
state={name:'',items:'',price:'',arr:[],错误:{name:'',items:'',price:''}
todoSubmit=(事件)=>
{
event.preventDefault()
让list=this.state.arr;
让tododata={name:this.state.name,items:this.state.items,price:this.state.price};
list.push(tododata);
this.setState({arr:list});
console.log(this.state.arr);
}
句柄=(事件)=>
{
常量{name,value}=event.target;
让errors=this.state.error;
开关(错误)
{
案例“name”:errors.name=value.length0&&{errors.items}
价格:
{errors.price.length>0&&{errors.price}
序号
名称
项目
价格
行动
{this.state.arr.map((数据,ind)=>
{ind+1}
{data.name}
{data.items}
{data.price}
this.deldata(ind)}>delete
)}
)
}
}
将默认值导出到olist2您好,请尝试下面的解决方案,如果有帮助,请告诉我:)非常感谢您的解释和帮助。你的解决方案奏效了!再次感谢@丁斯帕塔伊,不客气!我很高兴这对您有所帮助:)
updateValue = (e) => {
const { note } = this.state;
this.setState({
note: { ...note, [e.target.name]: e.target.value }
});
}
state={name:'',items:'',price:'',arr:[],errors:{name:'',items:'',price:''}}
todoSubmit=(event)=>
{
event.preventDefault()
let list=this.state.arr;
let tododata={name:this.state.name, items:this.state.items, price:this.state.price};
list.push(tododata);
this.setState({arr:list});
console.log(this.state.arr);
}
handle=(event)=>
{
const {name,value}=event.target;
let errors=this.state.error;
switch(errors)
{
case 'name':errors.name=value.length<2?"Name must be 2 character long":'';
case 'items':errors.items=value.length<2?"items must be 2 character long":'';
case 'price':errors.price=value.length<2?"price must be 2 character long":'';
}
this.setState({errors,[name]:value})
this.setState({[name]:value})
console.log(this.state);
}
deldata=(ind)=>
{
if (window.confirm('Do u want to delete'))
{
let list=this.state.arr;
list.splice(ind,1);
this.setState({arr:list});
}
// alert('do u want to delete');
}
render() {
const {errors}=this.state;
return (
<div>
<h1>ToDo List 2</h1>
<form className='container' onSubmit={this.todoSubmit}>
<div className="form-group col-md-4">
<label>Name:</label>
<input type="text" name="name" className='form-control' onChange={this.handle}/>
{errors.name.length>0 && <span className='alert alert-danger'>{errors.name}</span> }
</div>
<div className="form-group col-md-4" onChange={this.handle}>
<label>Items:</label>
<input type="text" name="items" class='form-control'/>
{errors.items.length>0 && <span className='alert alert-danger'>{errors.items}</span> }
</div>
<div className="form-group col-md-4" onChange={this.handle}>
<label>Price:</label>
<input type="text" name="price" class='form-control'/>
{errors.price.length>0 && <span className='alert alert-danger'>{errors.price}</span> }
</div>
<input type='Submit' value='Submit' class='btn btn-outline-success' />
<table class='table'>
<tr>
<th>S.no</th>
<th>Name</th>
<th>Items</th>
<th>Price</th>
<th>Action</th>
</tr>
{this.state.arr.map((data,ind)=>
<tr>
<td>{ind+1}</td>
<td>{data.name}</td>
<td>{data.items}</td>
<td>{data.price}</td>
<td><button class="btn btn-info btn-lg " onClick={()=>this.deldata(ind)}>delete </button></td>
</tr>
)}
</table>
</form>
</div>
)
}