Cannot find module "popper.js" Angular 5 Visual Studio 2017 asp.net core

Question

I updated my Angular's verision from 4 to 5. Below is the screenshot, I followed the instruction as per the link http://www.talkingdotnet.com/upgrade-angular-4-app-angular-5-visual-studio-2017/

package.json file

{
  "name": "VotingWebsite",
  "private": true,
  "version": "0.0.0",
  "scripts": {
    "test": "karma start ClientApp/test/karma.conf.js"
  },
  "devDependencies": {
    "@angular/animations": "5.2.1",
    "@angular/common": "5.2.1",
    "@angular/compiler": "5.2.1",
    "@angular/compiler-cli": "5.2.1",
    "@angular/core": "5.2.1",
    "@angular/forms": "5.2.1",
    "@angular/http": "5.2.1",
    "@angular/platform-browser": "5.2.1",
    "@angular/platform-browser-dynamic": "5.2.1",
    "@angular/platform-server": "5.2.1",
    "@angular/router": "5.2.1",
    "@ngtools/webpack": "1.9.5",
    "@types/chai": "4.1.1",
    "@types/jasmine": "2.8.5",
    "@types/webpack-env": "1.13.3",
    "angular2-router-loader": "0.3.5",
    "angular2-template-loader": "0.6.2",
    "aspnet-prerendering": "^3.0.1",
    "aspnet-webpack": "^2.0.1",
    "awesome-typescript-loader": "3.4.1",
    "popper.js": "^1.12.5",
    "bootstrap": "4.0.0",
    "chai": "4.1.2",
    "css": "2.2.1",
    "css-loader": "0.28.9",
    "es6-shim": "0.35.3",
    "event-source-polyfill": "0.0.12",
    "expose-loader": "0.7.4",
    "extract-text-webpack-plugin": "3.0.2",
    "file-loader": "1.1.6",
    "html-loader": "0.5.5",
    "isomorphic-fetch": "2.2.1",
    "jasmine-core": "2.9.1",
    "jquery": "3.3.1",
    "json-loader": "0.5.7",
    "karma": "2.0.0",
    "karma-chai": "0.1.0",
    "karma-chrome-launcher": "2.2.0",
    "karma-cli": "1.0.1",
    "karma-jasmine": "1.1.1",
    "karma-webpack": "2.0.9",
    "preboot": "6.0.0-beta.1",
    "raw-loader": "0.5.1",
    "reflect-metadata": "0.1.12",
    "rxjs": "5.5.6",
    "style-loader": "0.19.1",
    "to-string-loader": "1.1.5",
    "typescript": "2.6.2",
    "url-loader": "0.6.2",
    "webpack": "3.10.0",
    "webpack-hot-middleware": "2.21.0",
    "webpack-merge": "4.1.1",
    "zone.js": "0.8.20"
  }
}

I am getting an error as

Uncaught Error: Cannot find module "popper.js"
    at webpackMissingModule (vendor.js?v=g866IhqI_4JvgibiHgn9GiAXKfG42-s7C9LGGfxA0Tk:sourcemap:82252)
    at vendor.js?v=g866IhqI_4JvgibiHgn9GiAXKfG42-s7C9LGGfxA0Tk:sourcemap:82252
    at Object.<anonymous> (vendor.js?v=g866IhqI_4JvgibiHgn9GiAXKfG42-s7C9LGGfxA0Tk:sourcemap:82255)
    at __webpack_require__ (vendor.js?v=g866IhqI_4JvgibiHgn9GiAXKfG42-s7C9LGGfxA0Tk:sourcemap:21)
    at Object.<anonymous> (bootstrap.js from dll-reference vendor_19596f3f8868cecda14a:1)
    at __webpack_require__ (bootstrap acba0f7e8b1985fd75ba:678)
    at fn (bootstrap acba0f7e8b1985fd75ba:88)
    at Object.<anonymous> (process-update.js:146)
    at __webpack_require__ (bootstrap acba0f7e8b1985fd75ba:678)
    at fn (bootstrap acba0f7e8b1985fd75ba:88)

Webpack.config.js

const path = require('path');
const webpack = require('webpack');
const merge = require('webpack-merge');
const AngularCompilerPlugin = require('@ngtools/webpack').AngularCompilerPlugin;
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$/, use: isDevBuild ? ['awesome-typescript-loader?silent=true', 'angular2-template-loader', 'angular2-router-loader'] : '@ngtools/webpack' },
                { test: /\.html$/, 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')
            })
        ].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 AngularCompilerPlugin({
                tsConfigPath: './tsconfig.json',
                entryModule: path.join(__dirname, 'ClientApp/app/app.browser.module#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 AngularCompilerPlugin({
                tsConfigPath: './tsconfig.json',
                entryModule: path.join(__dirname, 'ClientApp/app/app.server.module#AppModule'),
                exclude: ['./**/*.browser.ts']
            })
        ]),
        output: {
            libraryTarget: 'commonjs',
            path: path.join(__dirname, './ClientApp/dist')
        },
        target: 'node',
        devtool: 'inline-source-map'
    });

    return [clientBundleConfig, serverBundleConfig];
};

It was working perfectly with angular 4 template in asp.net core Visual Studio 2017. When I update the package to Angular 5, I'm getting an error as described above.

I tried to google the solution, but not able to find the solution.

Answer 1

I fixed the same problem in my project by:

1) Adding popper.js to the package.json file (I see you already have this), and running "npm install":

"popper.js": "^1.12.9",

2) Adding an Import popper.js statement to the boot.browser.js file before the import bootstrap statement :

import 'popper.js';
import 'bootstrap';

Answer 2

对于较新版本的 Angular， npm install @popperjs/core成功了！

Answer 3

更新package.json文件后，您可能需要运行npm install 。