为什么带反引号的字符串插值对反应不起作用?
why string interpolation with backticks isn't working on react?
我在一个个人项目中工作,我试图实现一个字符串插值,但由于某种原因它不起作用并且抛出错误。
我正在使用 visual studio 代码,它抛出的错误如下:
- 属性 预期分配
- ';'预计(2 次)
- 预期的声明或声明
这是我放置特定插值的行:
newsection = {`${newsectionnmb}`:"placeholder"}
这是我的完整代码:
import React, { Component } from "react";
import { NavLink, match } from "react-router-dom";
import { withRouter } from "react-router-dom";
import axios from "axios";
class AddContent extends Component{
constructor(props) {
super(props)
this.state = {
name: "",
content: "",
courseName:"",
actualContent: [],
section:"NEW",
video: ""
}
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
componentDidMount() {
axios.get(`http://localhost:5000/course/id/${Number(this.props.match.params.id)}`)
.then( (response)=> {
this.setState({
courseName: response.data.name,
actualContent: response.data.content
});
if(this.props._id != response.data.adminId) {
this.props.history.push("/");
}
})
.catch(function (error) {
console.log(error);
alert("we couldn't fetch the course data, try again later by reloading the page")
})
}
handleChange(event) {
const target = event.target;
const value = target.value;
const name = target.name;
this.setState({
[name]: value
});
}
handleSubmit= (event)=> {
if (this.state.name !== "" ) {
if (this.state.section === "NEW") {
newsectionnmb = this.state.actualContent.length +1;
newsection = {`${newsectionnmb}`:"placeholder"}
}
event.preventDefault();
axios({
method: 'put',
url: `http://localhost:5000/course/add-content/${Number(this.props.match.params.id)}`,
data: {
content: this.state.content
}
})
}
}
render() {
let sectionlist = this.state.actualContent.length > 0
&& this.state.actualContent.map((item, i) => {
return (
<option key={i} value={item.name}>{item.name}</option>
)
}, this);
return (
<div className="courses">
{this.props.registered === true?
<div>
<form onSubmit={this.handleSubmit} className="Register">
<h1>Add guide</h1>
<h2>{this.state.courseName}</h2>
<p>quotation marks aren't allowed</p>
<div>
<input
name="name"
type="text"
onChange={this.handleChange}
placeholder="name"/>
</div>
<div>
<input
name="video"
type="text"
onChange={this.handleChange}
placeholder="URL for video"/>
</div>
<div>
<textarea
name="content"
type="text"
onChange={this.handleChange}
placeholder="content"/>
</div>
<label>select section:</label>
<select name="section" onChange={this.handleChange} className="select">
<option value="NEW">New Section</option>
{sectionlist}
</select>
<button type="submit" className="coursesub">Submit</button>
<NavLink exact to="/courses">Go back to course</NavLink>
</form>
</div>
:
<div>
<h1>Welcome to SSG courses app, to start using please login.</h1>
<NavLink exact to="/login">Login</NavLink>
</div>
}
</div>
)
}
}
export default withRouter(AddContent);
如果你想让newsection成为一个对象,应该这样做
newsection = {newsectionnmb:"placeholder"}
如果你想把它变成一个字符串,这应该适合你
newsection = `${newsectionnmb}:"placeholder"`
我在一个个人项目中工作,我试图实现一个字符串插值,但由于某种原因它不起作用并且抛出错误。 我正在使用 visual studio 代码,它抛出的错误如下:
- 属性 预期分配
- ';'预计(2 次)
- 预期的声明或声明
这是我放置特定插值的行:
newsection = {`${newsectionnmb}`:"placeholder"}
这是我的完整代码:
import React, { Component } from "react";
import { NavLink, match } from "react-router-dom";
import { withRouter } from "react-router-dom";
import axios from "axios";
class AddContent extends Component{
constructor(props) {
super(props)
this.state = {
name: "",
content: "",
courseName:"",
actualContent: [],
section:"NEW",
video: ""
}
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
componentDidMount() {
axios.get(`http://localhost:5000/course/id/${Number(this.props.match.params.id)}`)
.then( (response)=> {
this.setState({
courseName: response.data.name,
actualContent: response.data.content
});
if(this.props._id != response.data.adminId) {
this.props.history.push("/");
}
})
.catch(function (error) {
console.log(error);
alert("we couldn't fetch the course data, try again later by reloading the page")
})
}
handleChange(event) {
const target = event.target;
const value = target.value;
const name = target.name;
this.setState({
[name]: value
});
}
handleSubmit= (event)=> {
if (this.state.name !== "" ) {
if (this.state.section === "NEW") {
newsectionnmb = this.state.actualContent.length +1;
newsection = {`${newsectionnmb}`:"placeholder"}
}
event.preventDefault();
axios({
method: 'put',
url: `http://localhost:5000/course/add-content/${Number(this.props.match.params.id)}`,
data: {
content: this.state.content
}
})
}
}
render() {
let sectionlist = this.state.actualContent.length > 0
&& this.state.actualContent.map((item, i) => {
return (
<option key={i} value={item.name}>{item.name}</option>
)
}, this);
return (
<div className="courses">
{this.props.registered === true?
<div>
<form onSubmit={this.handleSubmit} className="Register">
<h1>Add guide</h1>
<h2>{this.state.courseName}</h2>
<p>quotation marks aren't allowed</p>
<div>
<input
name="name"
type="text"
onChange={this.handleChange}
placeholder="name"/>
</div>
<div>
<input
name="video"
type="text"
onChange={this.handleChange}
placeholder="URL for video"/>
</div>
<div>
<textarea
name="content"
type="text"
onChange={this.handleChange}
placeholder="content"/>
</div>
<label>select section:</label>
<select name="section" onChange={this.handleChange} className="select">
<option value="NEW">New Section</option>
{sectionlist}
</select>
<button type="submit" className="coursesub">Submit</button>
<NavLink exact to="/courses">Go back to course</NavLink>
</form>
</div>
:
<div>
<h1>Welcome to SSG courses app, to start using please login.</h1>
<NavLink exact to="/login">Login</NavLink>
</div>
}
</div>
)
}
}
export default withRouter(AddContent);
如果你想让newsection成为一个对象,应该这样做
newsection = {newsectionnmb:"placeholder"}
如果你想把它变成一个字符串,这应该适合你
newsection = `${newsectionnmb}:"placeholder"`