QZ giving errors on angular install and websocket not found

Question

I am trying to get my angular webapp working with a star sp 700 receipt printer and am trying to integrate qz-tray into my software for that reason. I am getting an error when trying to install @types/qz-tray which is displayed below. Also I get an error

unresolved variable websocket

on the line 23 and

unresolved variable api

on line 16.

Can someone please tell me how to fix this and if there is a better way of printing to either this or another receipt printer through angular?

import { Injectable } from '@angular/core';
import { from as fromPromise, Observable, throwError } from 'rxjs';
import { HttpErrorResponse } from '@angular/common/http';
import { catchError, map } from 'rxjs/operators';

import * as qz from 'qz-tray';
import { sha256 } from 'js-sha256';

@Injectable({
  providedIn: 'root'
})
export class PrinterService {

  //npm install qz-tray js-sha256 rsvp --save
  constructor() {
    qz.api.setSha256Type(data => sha256(data));
    qz.api.setPromiseType(resolver => new Promise(resolver));
  }
  // Get the list of printers connected
  getPrinters(): Observable<string[]> {
    console.log('+++++++++PrinterService+++++');
    return fromPromise(
      qz.websocket.connect().then(() => qz.printers.find())
    )
    map((printers: string[]) => printers)
      , catchError(this.errorHandler);
  }

  // Get the SPECIFIC connected printer
  getPrinter(printerName: string): Observable<string> {
    return fromPromise(
      qz.websocket.connect()
        .then(() => qz.printers.find(printerName))
    )
    map((printer: string) => printer)
      , catchError(this.errorHandler);
  }

  // Print data to chosen printer
  printData(printer: string, data: any): Observable<any> {
    const config = qz.configs.create(printer);

    return fromPromise(qz.print(config, data))
    map((anything: any) => anything)
      , catchError(this.errorHandler);
  }

  private errorHandler(error: HttpErrorResponse) {
    if (error.error instanceof ErrorEvent) {
      console.log(error.error);
      console.log('An error occurred:', error.status);
      return throwError(error.error);
    } else {
      console.log('An error occurred:', error.status);
      console.log(error.error);
      return throwError(error.error);
    }
  };
}

tresf · Answer 1 · 2020-01-15T18:19:30.017

unresolved variable websocket
unresolved variable api

These are both signs that qz-tray.js did not load properly.

The objects qz.api and qz.websocket are both part of the qz namespace. If they're not available, then qz was never imported properly.

Here's a working example of QZ Tray running in Angular: https://stackblitz.com/edit/angular-3h4cnv

The import line appears to be correct and matches that of the QZ Tray angular quickstart guide.
The import * as qz should be valid according to TypeScript guidelines on exporting the default export of a module however you can safely convert it to import { default as qz } from "qz-tray";

As a troubleshooting step, you can call:

console.log(qz);

If loaded properly, it should show something like this:

Another troubleshooting technique would be to remove and reinstall qz-tray using your preferred package manager npm uninstall qz-tray; npm install qz-tray, etc.

QZ giving errors on angular install and websocket not found

1 Answers1