How to Create a File Download Progress Bar in Angular 8
Downloading files is a common task for web applications. Whether it's a PDF, ZIP, or any other binary or text-based file, you want to make it accessible and user-friendly for your users. One way to do that is to create a file download progress bar that shows how much of the file has been downloaded and how long it will take to complete.
file download progress bar in angular 8
A file download progress bar can improve the user experience by providing feedback, reducing uncertainty, and increasing trust. It can also prevent users from canceling or interrupting the download process, which can cause errors or data loss.
In this article, you will learn how to create a file download progress bar in Angular 8 using three different options: using a simple HTML link, using HttpClient and RxJS, and using Angular Material Progress Bar. You will also learn the pros and cons of each option and some best practices for creating a file download progress bar in Angular 8.
Option 1: Using a Simple HTML Link
The simplest way to create a file download link in Angular is to use plain HTML with an anchor tag pointing to the file URL with the href attribute. The download attribute informs the browser that it should not follow the link but rather download the URL target. You can also specify its value in order to set the name of the file being downloaded.
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Angular 8 download file with Content-Disposition header
Angular 8 download file with Blob and saveAs method
Angular 8 download file with custom progress component
Angular 8 download file with RxJS operators and observables
Angular 8 download file with HTTP POST method and reportProgress option
Angular 8 download file with HTTP GET method and responseType blob
Angular 8 download file with HttpClient and HttpEvent interface
Angular 8 download file with HttpClient and HttpHeaders class
Angular 8 download file with HttpClient and HttpParams class
Angular 8 download file with HttpClient and HttpRequest class
Angular 8 download file with HttpClient and HttpResponse class
Angular 8 download file with HttpClient and HttpErrorResponse class
Angular 8 download file with HttpClient and HttpInterceptor interface
Angular 8 download file with HttpClient and HttpHandler interface
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Angular 8 download file with HttpClient and HttpTestingController class
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Angular 8 download file with HttpClient and HttpResponseBase class
Angular 8 download file with HttpClient and HttpResponseHeader class
Angular 8 download file with HttpClient and HttpSentEvent interface
Angular 8 download file with HttpClient and HttpHeaderResponse class
Angular 8 download file with HttpClient and HttpProgressEvent interface
Angular 8 download file with HttpClient and HttpUserEvent interface
Angular 8 download file with HttpClient and HttpHeadersInit type alias
Angular 8 download file with HttpClient and HttpRequestInit type alias
Angular 8 download file with HttpClient and HttpResponseInit type alias
Angular 8 download file with HttpClient and HttpEventInit type alias
Angular 8 download file with HttpClient and HttpHeadersOptions interface
Angular 8 download file with HttpClient and HttpRequestOptions interface
Angular 8 download file with HttpClient and HttpResponseOptions interface
Angular 8 download file with HttpClient and HttpEventOptions interface
Angular 8 download file with HttpClient and HttpHeadersUpdate interface
Angular 8 download file with HttpClient and HttpRequestUpdate interface
Angular 8 download file with HttpClient and HttpResponseUpdate interface
Angular 8 download file with HttpClient and HttpEventUpdate interface
How to show percentage of downloaded files in angular progress bar?
How to cancel or pause a downloading files in angular?
How to handle errors or exceptions while downloading files in angular?
How to test or mock downloading files in angular?
For example, you can create a download link for an archive.zip file like this:
<a href="/downloads/archive.zip" download="archive.zip">archive.zip</a>
You can bind any of these attributes with Angular in order to set the URL and filename dynamically:
<a [href]="download.url" [download]="download.filename"> download.filename </a>
Older browsers, like Internet Explorer, might not recognize the download attribute. For those cases, you can open the download in a new browser tab with the target attribute set to _blank. Make sure though to always include rel="noopener noreferrer" when you're using target="_blank" so you're not opening yourself up to security vulnerabilities.
<a [href]="download.url" target="_blank" rel="noopener noreferrer"> download.filename </a>
If there's no download attribute, the filename for your download will solely depend on the HTTP header Content-Disposition sent by the server that's providing the file. The information from this header might also take precedence even if the download attribute is present.
A link-based solution conforms well to HTML standards and lets the browser do most of the work. However, if you want more control over the download and would like to display some custom progress indicator, you can also download files via Angular's HttpClient.
Option 2: Using HttpClient and RxJS
A file is best represented as a Blob in the browser:
The Blob object represents a A file is best represented as a Blob in the browser:
The Blob object represents a blob, which is a file-like object of immutable, raw data; they can be read as text or binary data, or converted into a ReadableStream so its methods can be used for processing the data.
To download a file as a Blob, you can use the HttpClient service from Angular's common HTTP module. You need to inject it into your component or service and then perform a GET request with the responseType option set to blob:
import HttpClient from '@angular/common/http'; constructor(private http: HttpClient) downloadFile(url: string) return this.http.get(url, responseType: 'blob' );
This will return an Observable that you can subscribe to and get the file data. However, this will not give you any information about the download progress. To get that, you need to use two more options: reportProgress and observe.
The reportProgress option is a boolean that indicates whether or not the HttpClient should track and report the progress of the request. The observe option is a string that specifies what type of events you want to observe. The possible values are body, response, and events. The default value is body, which means you only get the final response body. The response value means you get the full HttpResponse object with headers and status. The events value means you get all the HttpEvents that occur during the request lifecycle, such as sent, upload progress, response header, download progress, and response.
To get the download progress events, you need to set both reportProgress and observe to true and events respectively:
downloadFile(url: string) return this.http.get(url, responseType: 'blob', reportProgress: true, observe: 'events' );
This will return an Observable that you can subscribe to and filter by the HttpEventType.DownloadProgress enum. This event has two properties: loaded and total. The loaded property is the number of bytes that have been downloaded so far. The total property is the total number of bytes to be downloaded, if known. You can use these properties to calculate the percentage of the download progress and display it in your UI.
Once the download is complete, you will get an HttpEventType.Response event with the Blob data in its body property. You can then use the saveAs function from FileSaver.js, a library that implements the HTML5 saveAs() FileSaver interface in browsers that do not natively support it, to save the file to disk. You can also use the filename from the Content-Disposition header or from your own logic.
Here is an example of how to use HttpClient and RxJS to download a file and show its progress:
import Component from '@angular/core'; import HttpClient, HttpEventType from '@angular/common/http'; import saveAs from 'file-saver'; @Component( selector: 'app-download', template: ` <div> <button (click)="downloadFile()">Download</button> <p *ngIf="progress"> progress %</p> </div> ` ) export class DownloadComponent progress: number; constructor(private http: HttpClient) downloadFile() this.http .get('/downloads/archive.zip', responseType: 'blob', reportProgress: true, observe: 'events' ) .subscribe((event) => if (event.type === HttpEventType.DownloadProgress) this.progress = Math.round((100 * event.loaded) / event.total); else if (event.type === HttpEventType.Response) const filename = event.headers .get('content-disposition') .split(';')[1] .split('=')[1] .replace(/"/g, ''); saveAs(event.body, filename); );
Using HttpClient and RxJS gives you more control over the download process and allows you to create custom progress indicators. However, if you want a ready-made solution that follows Angular's Material Design guidelines, you can also use Angular Material Progress Bar.
Option 3: Using Angular Material Progress Bar
Angular Material Progress Bar is a component that provides a horizontal bar to indicate the progress of an operation. It supports four modes: determinate, indeterminate, buffer, and query. The determinate mode is used when the percentage of the operation is known. The indeterminate mode is used when the percentage of the operation is unknown Angular Material Progress Bar is a component that provides a horizontal bar to indicate the progress of an operation. It supports four modes: determinate, indeterminate, buffer, and query. The determinate mode is used when the percentage of the operation is known. The indeterminate mode is used when the percentage of the operation is unknown or infinite. The buffer mode is used when the percentage of the operation is known but there is some additional loading that is not yet completed. The query mode is used when the progress of the operation depends on an external factor, such as a server response.
To use Angular Material Progress Bar, you need to install and import the MatProgressBarModule from @angular/material/progress-bar:
npm install --save @angular/material @angular/cdk @angular/animations import MatProgressBarModule from '@angular/material/progress-bar'; @NgModule( imports: [MatProgressBarModule] ) export class AppModule
Then, you can use the mat-progress-bar component in your template with the mode and value inputs. The mode input can be one of the four modes mentioned above. The value input can be a number between 0 and 100 that represents the percentage of the progress. For example, you can create a determinate progress bar like this:
<mat-progress-bar mode="determinate" [value]="progress"></mat-progress-bar>
You can also use the color input to change the color of the progress bar. The possible values are primary, accent, and warn, which correspond to the theme colors defined by Angular Material. For example, you can create a red progress bar like this:
<mat-progress-bar mode="determinate" [value]="progress" color="warn"></mat-progress-bar>
You can also style and customize the appearance of the progress bar using CSS classes and variables. For example, you can change the height, background color, and animation duration of the progress bar like this:
<style> .custom-progress-bar height: 20px; background-color: lightgray; --mat-progress-bar-animation-duration: 2s; </style> <mat-progress-bar mode="determinate" [value]="progress"></mat-progress-bar>
Using Angular Material Progress Bar gives you a ready-made solution that follows Angular's Material Design guidelines and provides a consistent look and feel for your application. However, you might need to customize it further to suit your specific needs and preferences.
Conclusion
In this article, you learned how to create a file download progress bar in Angular 8 using three different options: using a simple HTML link, using HttpClient and RxJS, and using Angular Material Progress Bar. You also learned the pros and cons of each option and some best practices for creating a file download progress bar in Angular 8.
Here is a summary of the main points and comparison of the options:
Option Pros Cons --- --- --- HTML link Simple and standard No progress indicator or control HttpClient and RxJS More control and customizability More code and complexity Angular Material Progress Bar Ready-made and consistent Less flexibility and customization Depending on your requirements and preferences, you can choose any of these options to create a file download progress bar in Angular 8. However, some general recommendations and best practices are:
Use descriptive filenames and URLs for your downloads
Use appropriate MIME types and Content-Disposition headers for your downloads
Use HTTPS for secure downloads
Handle errors and exceptions gracefully
Test your downloads on different browsers and devices
FAQs
How do I cancel a file download in Angular?
If you are using HttpClient and RxJS to download a file, you can cancel the download by unsubscribing from the Observable returned by the GET request. This will abort the underlying XMLHttpRequest and stop the download.
How do I resume a file download in Angular?
If you are using HttpClient and RxJS to download a file, you can resume a partial download by using the Range header in your GET request. This header specifies the byte range of the file that you want to download. For example, if you have downloaded 50% of a 100 MB file, you can resume the download from byte 50,000,001 to byte 100,000,000 by setting the Range header to bytes=50000001-100000000 If you are using HttpClient and RxJS to download a file, you can resume a partial download by using the Range header in your GET request. This header specifies the byte range of the file that you want to download. For example, if you have downloaded 50% of a 100 MB file, you can resume the download from byte 50,000,001 to byte 100,000,000 by setting the Range header to bytes=50000001-100000000.
However, this requires that the server supports the Range header and returns a 206 Partial Content response with the Content-Range header indicating the byte range of the partial content. Not all servers support this feature, so you might need to check the server capabilities before resuming a download.
How do I upload a file in Angular?
If you want to upload a file in Angular, you can use the HttpClient service again, but this time with a POST or PUT request instead of a GET request. You also need to use a FormData object to append the file data and any other parameters you want to send to the server. For example, you can upload a file like this:
import HttpClient from '@angular/common/http'; constructor(private http: HttpClient) uploadFile(file: File) const formData = new FormData(); formData.append('file', file, file.name); formData.append('otherParam', 'someValue'); return this.http.post('/uploads', formData);
This will return an Observable that you can subscribe to and get the server response. You can also use the reportProgress and observe options to get the upload progress events, similar to the download progress events.
How do I test a file download in Angular?
If you want to test a file download in Angular, you can use tools like Jasmine and Karma to write unit tests and end-to-end tests for your components and services that handle file downloads. You can also use tools like Protractor and Cypress to automate browser interactions and simulate user actions like clicking on download links or buttons.
However, testing file downloads can be challenging because different browsers handle downloads differently and might not expose the download status or events to JavaScript. You might need to use some workarounds or mock data to test your file download functionality. For example, you can use spyOn or stub methods from Jasmine or Sinon.js to mock the HttpClient service or the saveAs function and verify that they are called with the correct arguments. You can also use Blob URLs or data URLs instead of real URLs to create mock files for testing.
How do I create a custom file download progress bar in Angular?
If none of the options mentioned above suit your needs or preferences, you can always create your own custom file download progress bar in Angular. You can use HTML, CSS, and JavaScript to create any design or animation you want for your progress bar. You can also use Angular's directives, components, pipes, and services to make your progress bar reusable, configurable, and interactive.
For example, you can create a custom progress bar component that takes an input value for the percentage of the progress and displays it in a circular shape with some text and icons. You can then use this component in your template wherever you want to show a file download progress bar. You can also use Angular's ChangeDetectionStrategy and ChangeDetectorRef to optimize the performance of your component and avoid unnecessary change detection cycles. 44f88ac181