Question

在下面的代码中，当我通过解构声明变量字符时

const { characters } = this.state;

我收到意外的令牌错误。

import React, { Component } from "react";
import Table from "./Table";
class App extends Component {
  state = {
    characters: [
      {
        name: "Charlie",
        job: "Janitor"
      },
      {
        name: "Mac",
        job: "Bouncer"
      },
      {
        name: "Dee",
        job: "Aspring actress"
      },
      {
        name: "Dennis",
        job: "Bartender"
      }
    ]
  };
  removeCharacter = index => {
    const { characters } = this.state;

    this.setState({
      characters: characters.filter((character, i) => {
        return i !== index;
      })
    });
  };
   const { characters } = this.state;
  render() {
   
    return (
      <React.Fragment>
        <div className="App">
          <h1>Hello, React!</h1>
        </div>

        <div className="container">
          <Table
            characterData={characters}
            removeCharacter={this.removeCharacter}
          />
        </div>
      </React.Fragment>
    );
  }
}

export default App;

这是代码的沙盒：sandbox with the error, look at the app.js file

当我将声明放入render函数中时，没有问题，查看correct代码沙箱。

同样，当我在render函数（位于App.js文件的函数之外）中创建变量时，没有使用const或例如：

x=1;

当我在render函数中以this.x的形式使用它时，它工作正常，但是当我用let，const或var声明它时，会抛出意外的令牌错误。

您如何解释这种行为？

Answer 1

您已在render方法之外破坏了字符。

import React, { Component } from "react";
import Table from "./Table";
class App extends Component {
  state = {
    characters: [
      {
        name: "Charlie",
        job: "Janitor"
      },
      {
        name: "Mac",
        job: "Bouncer"
      },
      {
        name: "Dee",
        job: "Aspring actress"
      },
      {
        name: "Dennis",
        job: "Bartender"
      }
    ]
  };
  removeCharacter = index => {
    const { characters } = this.state;

    this.setState({
      characters: characters.filter((character, i) => {
        return i !== index;
      })
    });
  };
  render() {
    const { characters } = this.state;
    return (
      <React.Fragment>
        <div className="App">
          <h1>Hello, React!</h1>
        </div>

        <div className="container">
          <Table
            characterData={characters}
            removeCharacter={this.removeCharacter}
          />
        </div>
      </React.Fragment>
    );
  }
}

export default App;

在component类内部和render函数外部声明变量以在react中的render函数内部使用变量时出错

1 个答案: