Aleksandr Volkov's questions

const a = {};

    function clear(obj) {
        obj.x = 40;
        obj = null
    }
    clear (a);

    console.log(a)

为什么输出到控制台{x: 40}而不是null？

有一些功能sum(a, b)。通过包装函数（wrapper(func)）我想在初始函数中添加一个自定义属性calls，让它成为一个条件数组。通过添加此属性func.calls或this.calls调用此属性时，输出undefined. 这是为什么？如何wrapper(func)正确设置此属性？

function sum(a, b) {
  alert(a + b);
}

function wrapper(func) {
  return function(a, b) {
    //func.calls = [1,2,3];
    this.calls = [1, 2, 3]
    func(a, b);
  };
}

sum = wrapper(sum);

console.log(sum.calls); //undefined

我通过 webpack html 形成 form-elements.html 页面。我在这个页面的JS文件中连接了item-quantity-dropdown插件：

import $ from "jquery";
import './form-elements.scss'
import 'item-quantity-dropdown/lib/item-quantity-dropdown.min';
import 'item-quantity-dropdown/lib/item-quantity-dropdown.min.css';

$(document).ready(() => {
  $('.iqdropdown').iqDropdown({});
});

webpack.config.js 文件

const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const webpack = require('webpack');

let globule = require('globule');
let mode = 'development';
if ( process.env.NODE_ENV === 'production' ) {
  mode = 'production'
}
console.log(mode + ' mode');

const paths = globule.find(["src/pages/**/*.pug"])

module.exports = {
  mode: mode,
  entry: {
    'colors-types': './src/pages/colors-types/colors-types.js',
    'form-elements': './src/pages/form-elements/form-elements.js',
  },
  output: {
    filename: '[name],[contenthash].js',
    assetModuleFilename: "assets/[hash][ext][query]",
    clean: true,
  },
  devtool: 'source-map',
  optimization: {
    splitChunks: {
      chunks: "all",
    },
  },
  plugins: [
    new webpack.ProvidePlugin({
      $: 'jquery',
      '$': 'jquery',
    }),
    new MiniCssExtractPlugin({
      filename: '[name].[contenthash].css'
}),
  //   new HtmlWebpackPlugin({
  //   template: "./src/pages/colors-types/colors-types.pug"
  // }),
    ...paths.map((path) => {
      return new HtmlWebpackPlugin( {
        template: path,
        filename: `${path.split(/\/|.pug/).splice(-2, 1)}.html`,
      });
    })],
  module: {
    rules: [
      {
        test: /\.html$/i,
        loader: "html-loader",
      },
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          (mode === 'development') ? "style-loader" : MiniCssExtractPlugin.loader,
          "css-loader",
          {
            loader: "postcss-loader",
            options: {
              postcssOptions: {
                plugins: [
                  [
                    "postcss-preset-env",
                    {
                      //Options
                    }
                  ]
                ]
              }
            }
          },
          "sass-loader",
        ]
      },
      {
        test: /\.(png|svg|jpg|jpeg|gif)$/i,
        type: 'asset/resource',
      },
      {
        test: /\.(woff|woff2|eot|ttf|otf)$/i,
        type: "asset/resource",
      },
      {
        test: /\.pug$/,
        loader: 'pug-loader',
        exclude: /(node-modules|bower_components)/,
      },
      {
        test: /\.m?js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env']
          }
        }
      },
    ]
  },

}

当我生成页面时，form-elements.html我在控制台中收到以下错误：

ReferenceError：未定义 jQuery

可能是什么问题呢？