Uncaught ReferenceError: Popper is not defined - with Bootstrap 4 and Webpack 3.8.1

Question

我在 .NET Core 2.0 中使用 Visual Studio 2017 Angular 模板。该模板有许多我已经更新的旧依赖项，包括 Angular 5.0.0。运行带有 Bootstrap 3.x.x 的原始模板有效。但是，使用 Bootstrap 4.0.0-beta.2 会导致以下错误：

Uncaught ReferenceError: Popper is not defined

我已尽我所能按照此处的说明进行操作：

http://getbootstrap.com/docs/4.0/getting-started/webpack/

我看过这个问题：

根据那里列出的解决方案，我必须在 bootstrap 之前注册 popper 或使用 boostrap 的最小版本，因为它已经带有 popper。但是，我正在使用 webpack 2.5.1（我刚刚在学习），我不知道如何在 webpack.config.js 文件中实现这些解决方案中的任何一个作为模板的一部分提供，包括由 boostrap-webpack 文档调用的修改。

webpack.config.js

const path = require('path');
const webpack = require('webpack');
const merge = require('webpack-merge');
const AotPlugin = require('@ngtools/webpack').AotPlugin;
const CheckerPlugin = require('awesome-typescript-loader').CheckerPlugin;

module.exports = (env) => {
    // Configuration in common to both client-side and server-side bundles
    const isDevBuild = !(env && env.prod);
    const sharedConfig = {
        stats: { modules: false },
        context: __dirname,
        resolve: { extensions: ['.js', '.ts'] },
        output: {
            filename: '[name].js',
            publicPath: 'dist/' // Webpack dev middleware, if enabled, handles requests for this URL prefix
        },
        module: {
            rules: [
                { test: /\.ts$/, include: /ClientApp/, use: isDevBuild ? ['awesome-typescript-loader?silent=true', 'angular2-template-loader'] : '@ngtools/webpack' },
                { test: /\.html$/, use: 'html-loader?minimize=false' },
                { test: /\.css$/, use: ['to-string-loader', isDevBuild ? 'css-loader' : 'css-loader?minimize'] },
                { test: /\.(png|jpg|jpeg|gif|svg)$/, use: 'url-loader?limit=25000' }
            ]
        },
        plugins: [new CheckerPlugin()]
    };

    // Configuration for client-side bundle suitable for running in browsers
    const clientBundleOutputDir = './wwwroot/dist';
    const clientBundleConfig = merge(sharedConfig, {
        entry: { 'main-client': './ClientApp/boot.browser.ts' },
        output: { path: path.join(__dirname, clientBundleOutputDir) },
        plugins: [
            new webpack.DllReferencePlugin({
                context: __dirname,
                manifest: require('./wwwroot/dist/vendor-manifest.json')
            }),
            new webpack.ProvidePlugin({
                $: 'jquery',
                jQuery: 'jquery',
                'window.jQuery': 'jquery',
                Popper: ['popper.js', 'default'],
                // In case you imported plugins individually, you must also require them here:
                //Util: "exports-loader?Util!bootstrap/js/dist/util",
                //Dropdown: "exports-loader?Dropdown!bootstrap/js/dist/dropdown"
            })
        ].concat(isDevBuild ? [
            // Plugins that apply in development builds only
            new webpack.SourceMapDevToolPlugin({
                filename: '[file].map', // Remove this line if you prefer inline source maps
                moduleFilenameTemplate: path.relative(clientBundleOutputDir, '[resourcePath]') // Point sourcemap entries to the original file locations on disk
            })
        ] : [
                // Plugins that apply in production builds only
                new webpack.optimize.UglifyJsPlugin(),
                new AotPlugin({
                    tsConfigPath: './tsconfig.json',
                    entryModule: path.join(__dirname, 'ClientApp/app/app.module.browser#AppModule'),
                    exclude: ['./**/*.server.ts']
                })
            ])
    });

    // Configuration for server-side (prerendering) bundle suitable for running in Node
    const serverBundleConfig = merge(sharedConfig, {
        resolve: { mainFields: ['main'] },
        entry: { 'main-server': './ClientApp/boot.server.ts' },
        plugins: [
            new webpack.DllReferencePlugin({
                context: __dirname,
                manifest: require('./ClientApp/dist/vendor-manifest.json'),
                sourceType: 'commonjs2',
                name: './vendor'
            })
        ].concat(isDevBuild ? [] : [
            // Plugins that apply in production builds only
            new AotPlugin({
                tsConfigPath: './tsconfig.json',
                entryModule: path.join(__dirname, 'ClientApp/app/app.module.server#AppModule'),
                exclude: ['./**/*.browser.ts']
            })
        ]),
        output: {
            libraryTarget: 'commonjs',
            path: path.join(__dirname, './ClientApp/dist')
        },
        target: 'node',
        devtool: 'inline-source-map'
    });

    return [clientBundleConfig, serverBundleConfig];
};

此外，这是作为模板的一部分提供的主要入口点文件 boot.browser.ts：

import 'reflect-metadata';
import 'zone.js';
import 'bootstrap';
import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule } from './app/app.module.browser';

if (module.hot) {
    module.hot.accept();
    module.hot.dispose(() => {
        // Before restarting the app, we create a new root element and dispose the old one
        const oldRootElem = document.querySelector('app');
        const newRootElem = document.createElement('app');
        oldRootElem!.parentNode!.insertBefore(newRootElem, oldRootElem);
        modulePromise.then(appModule => appModule.destroy());
    });
} else {
    enableProdMode();
}

// Note: @ng-tools/webpack looks for the following expression when performing production
// builds. Don't change how this line looks, otherwise you may break tree-shaking.
const modulePromise = platformBrowserDynamic().bootstrapModule(AppModule);

Answer 1

尝试在 bootstrap 之前而不是在

之后包括 Popper.js

 "../node_modules/popper.js/dist/umd/popper.min.js",
 "../node_modules/bootstrap/dist/js/bootstrap.min.js"

Answer 2

我终于找到了解决错误的方法。我在主入口点 boot.browser.ts 文件中使用了以下几行：

import * as $ from 'jquery';

//These two lines didn't remove the error
//import Popper from 'popper.js';
//import 'bootstrap';

//This one did remove the error. The bundle version of bootstrap includes popper in the correct order (according to the docs)
import 'bootstrap/dist/js/bootstrap.bundle.js';

有趣的是，bootstrap github (https://github.com/twbs/bootstrap/issues/24648) 中的建议代码是将此行用于 jquery 导入：

import $ from 'jquery'

而不是

import * as $ from 'jquery'

但是前者导致了这个错误：

Could not find a declaration file for module 'jquery'

但是，我不知道这两条线有什么区别

Answer 3

我安装了一个特定版本的 popper.js 我知道它正在使用 bootstrap 4.0.0-beta，就像这样：

npm install popper.js@1.12.5 --save-dev

然后我只需要像这样将它添加到我的 webpack.config.vendor.js 中：

new webpack.ProvidePlugin(
            { 
                $: 'jquery', 
                jQuery: 'jquery', // }, Maps these identifiers to the jQuery package (because Bootstrap expects it to be a global variable)
                jquery: 'jquery',
                'window.jQuery': 'jquery',
                Popper: 'popper.js/dist/umd/popper.js'                     
            }                
        ),

而且我不再收到 Uncaught ReferenceError: Popper is not defined 错误。

我没有更改代码，只更改了 webpack 和 npm。

Uncaught ReferenceError: Popper is not defined - with Bootstrap 4 and Webpack 3.8.1

Uncaught ReferenceError: Popper is not defined - with Bootstrap 4 and Webpack 3.8.1

twitter-bootstrap

webpack

visual-studio-2017

asp.net-core-2.0

angular