ngx-extended-pdf-viewer with angular 通用（预渲染）

Question

I have used ngx-extended-pdf-viewer in my Angular app to show a PDF catalog (The PDF catalog is on a locally folder). It works fine locally but when I try to prerender the app, I am getting this error: ERROR while prerendering

Here is the log file error:

0 info it worked if it ends with ok
1 verbose cli [
1 verbose cli   'C:\\Program Files\\nodejs\\node.exe',
1 verbose cli   'C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js',
1 verbose cli   'run',
1 verbose cli   'prerender'
1 verbose cli ]
2 info using npm@6.14.8
3 info using node@v12.19.0
4 verbose run-script [ 'prerender' ]
5 info lifecycle capcondo-angular@0.0.0~prerender: capcondo-angular@0.0.0
6 verbose lifecycle capcondo-angular@0.0.0~prerender: unsafe-perm in lifecycle true
7 verbose lifecycle capcondo-angular@0.0.0~prerender: PATH: C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\node-gyp-bin;D:\travail\Capcondo-angular\node_modules\.bin;C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\bin;C:\Users\ALA EDDINE\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0;C:\WINDOWS\System32\OpenSSH;C:\Program Files\nodejs;C:\Program Files\Git\cmd;C:\Program Files\dotnet;C:\Users\ALA EDDINE\AppData\Local\Microsoft\WindowsApps;C:\Users\ALA EDDINE\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\ALA EDDINE\AppData\Roaming\npm;C:\Program Files\heroku\bin
8 verbose lifecycle capcondo-angular@0.0.0~prerender: CWD: D:\travail\Capcondo-angular
9 silly lifecycle capcondo-angular@0.0.0~prerender: Args: [ '/d /s /c', 'ng run Capcondo-angular:prerender' ]
10 silly lifecycle capcondo-angular@0.0.0~prerender: Returned: code: 1  signal: null
11 info lifecycle capcondo-angular@0.0.0~prerender: Failed to exec prerender script
12 verbose stack Error: capcondo-angular@0.0.0 prerender: `ng run Capcondo-angular:prerender`
12 verbose stack Exit status 1
12 verbose stack     at EventEmitter.<anonymous> (C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\index.js:332:16)
12 verbose stack     at EventEmitter.emit (events.js:314:20)
12 verbose stack     at ChildProcess.<anonymous> (C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\lib\spawn.js:55:14)
12 verbose stack     at ChildProcess.emit (events.js:314:20)
12 verbose stack     at maybeClose (internal/child_process.js:1021:16)
12 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:286:5)
13 verbose pkgid capcondo-angular@0.0.0
14 verbose cwd D:\travail\Capcondo-angular
15 verbose Windows_NT 10.0.19042
16 verbose argv "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "run" "prerender"
17 verbose node v12.19.0
18 verbose npm  v6.14.8
19 error code ELIFECYCLE
20 error errno 1
21 error capcondo-angular@0.0.0 prerender: `ng run Capcondo-angular:prerender`
21 error Exit status 1
22 error Failed at the capcondo-angular@0.0.0 prerender script.
22 error This is probably not a problem with npm. There is likely additional logging output above.
23 verbose exit [ 1, true ]

Here is my server.ts file:

(global as any).WebSocket = require('ws');
(global as any).XMLHttpRequest = require('xhr2');

const domino = require('domino');
const fs = require('fs');
const path = require('path');
const distFolder = join(process.cwd(), 'dist/Capcondo-angular/browser');
const template = fs.readFileSync(path.join(distFolder, 'index.html')).toString();
const win = domino.createWindow(template.toString());
global['window'] = win;
global['document'] = win.document;
global['self'] = win
global['IDBIndex'] = win.IDBIndex
global['document'] = win.document
global['navigator'] = win.navigator
global['getComputedStyle'] = win.getComputedStyle;

import 'zone.js/dist/zone-node';

import { ngExpressEngine } from '@nguniversal/express-engine';
import * as express from 'express';
import { join } from 'path';

import { AppServerModule } from './src/main.server';
import { APP_BASE_HREF } from '@angular/common';
import { existsSync } from 'fs';

// The Express app is exported so that it can be used by serverless Functions.
export function app(): express.Express {
  const server = express();
  let distFolder = join(process.cwd(), 'browser');
  if (!existsSync(distFolder)) {
    distFolder = join(process.cwd(), 'dist/Capcondo-angular/browser');
  }
  const indexHtml = existsSync(join(distFolder, 'index.original.html')) ? 'index.original.html' : 'index';

  // Our Universal express-engine (found @ https://github.com/angular/universal/tree/master/modules/express-engine)
  server.engine('html', ngExpressEngine({
    bootstrap: AppServerModule,
  }));

  server.set('view engine', 'html');
  server.set('views', distFolder);

  // Example Express Rest API endpoints
  // server.get('/api/**', (req, res) => { });
  // Serve static files from /browser
  server.get('*.*', express.static(distFolder, {
    maxAge: '1y'
  }));

  // All regular routes use the Universal engine
  server.get('*', (req, res) => {
    res.render(indexHtml, { req, providers: [{ provide: APP_BASE_HREF, useValue: req.baseUrl }] });
  });

  return server;
}

function run(): void {
  const port = process.env.PORT || 4000;

  // Start up the Node server
  const server = app();
  server.listen(port, () => {
    console.log(`Node Express server listening on http://localhost:${port}`);
  });
}

// Webpack will replace 'require' with '__webpack_require__'
// '__non_webpack_require__' is a proxy to Node 'require'
// The below code is to ensure that the server is run only when not requiring the bundle.
declare const __non_webpack_require__: NodeRequire;
const mainModule = __non_webpack_require__.main;
const moduleFilename = mainModule && mainModule.filename || '';
if (moduleFilename === __filename || moduleFilename.includes('iisnode')) {
  run();
}

export * from './src/main.server';

I have already imported "NgxExtendedPdfViewerModule" in the app.module.ts and "NgxExtendedPdfViewerServerModule" in the app.server.module.ts.

Thank you in advance for your support!

Answer 1

Looks like you have use document global object directly in your code, which would break the universal and pre-rendering. You have 2 options:

1. using if(isPlatformBrowser(this.platformId)) check and put the code that uses browser's document object in it.
2. use dependency injection for mocking the document object. Angular has a built-in token for document which you can import from: @angular/common Then inject it like this:

@Inject(DOCUMENT) private readonly documentRef: Document

Then where you are using document object, simply replace it with: this.documentRef

I prefer the second approach

For more information read these articles:
Global objects in Angular
Angular Universal: real app problems