您好,我是React和编码的新手.我正在关注在线教程以学习React并遇到错误

./src/components/counter.jsx Line 24:  'product' is not defined  no-undef 

您能否简单地解释出什么问题了,所以我知道如何解决这个问题,下次遇到它时可以解决.

我仔细阅读了所有有关*的相关问题,但仍无法解决,如果我错过了回答此问题的问题,请链接它.
我过去曾犯过这个错误,但通常这只是因为我有错字(例如大写字母而不是小写字母)或未正确输入某些内容,但是据我所知这次不是这种情况.
我的代码与视频中的代码没有区别.

=== index.js ===

import React from "react";
import ReactDOM from "react-dom";
import "./index.css";
//import App from "./App";
import * as serviceWorker from "./serviceWorker";
import "bootstrap/dist/css/bootstrap.css";
import Counters from "./components/Counters";

ReactDOM.render(<Counters />, document.getElementById("root"));
serviceWorker.unregister();

=== counter.jsx ===

import React, { Component } from "react";

class Counter extends Component {
  state = {
    count: 0
  };

  handleIncrement = product => {
    console.log(product);
    this.setState({ count: this.state.count + 1 });
  };

  render() {
    return (
      <div>
        <span className={this.getBadgeClasses()}>{this.formatCount()}</span>
        <button
          onClick={() => this.handleIncrement(product)} //this is the line with the error
          className="btn btn-secondary btn-sm"
        >
          Increment
        </button>
      </div>
    );
  }

  getBadgeClasses() {
    let classes = "badge m-2 badge-";
    classes += this.state.count === 0 ? "warning" : "primary";
    return classes;
  }

  formatCount() {
    const { count } = this.state;
    return count === 0 ? "Zero" : count;
  }
}

export default Counter;

=== counters.jsx ===

import React, { Component } from "react";
import Counter from "./counter";

class Counters extends Component {
  state = {};
  render() {
    return (
      <div>
        <Counter />
        <Counter />
        <Counter />
        <Counter />
      </div>
    );
  }
}

export default Counters;

预期的输出是,当我运行它并转到网页时,它具有可以按的按钮和旁边的计数器,这些计数器将显示已被按下的次数.

实际发生的是,当我转到页面时,它显示以下内容：

Failed to compile

./src/index.js

Cannot find file: 'Counters.jsx' does not match the corresponding name on disk: './src/components/counters.jsx'.
This error occurred during the build time and cannot be dismissed.

解决方法:

onClick={() => this.handleIncrement(product)}

在执行此操作时,产品不存在.该变量尚未在任何地方声明或分配,因此未定义消息.

此消息是像eslint这样的短绒的产物,其中：

is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code, with the goal of making code more consistent and avoiding bugs.

短绒可以配置为发出警告和错误,并且在用作构建或编译过程的一部分时,可以配置为中止编译.

我不确定这里的意图是什么,但是您可以改为使用onClick = {this.handleIncrement},它将增加您的计数器.