Angular Image Upload Made Easy

Uploading images basically is a two-step process:

1. Select a file

• Send it to a server

Selecting a file requires us to have a <input type="file"> element in the Angular component template.

The key thing is to react to file changes made by the user. A change occurs if the user selects a file which differs from the currently selected one (null initially).

We can react to changes like this:

<input type="file" (change)="onFileChanged($event)">

In the component TypeScript file, we could get access to the file like this:

export class MyFileUploadComponent {
  onFileChanged(event) {
    const file = event.target.files[0]
  }
}

If you want to take a more elegant route and hide the file picker, you could implement the following code in your template:

<input
  style="display: none"
  type="file" (change)="onFileChanged($event)"
  #fileInput>
<button (click)="fileInput.click()">Select File</button>

You can of course also add an additional button which should then start the upload process:

<input
  style="display: none"
  type="file" (change)="onFileChanged($event)"
  #fileInput>
<button (click)="fileInput.click()">Select File</button>
<button (click)="onUpload()">Upload!</button>

In the component TypeScript file, you could handle it like this:

export class MyFileUploadComponent {
  selectedFile: File

  onFileChanged(event) {
    this.selectedFile = event.target.files[0]
  }

  onUpload() {
    // upload code goes here
  }
}

We have the file, to send it to the server, we can use the Angular HttpClient.

We can either send the file as a binary or as part of a FormData object - whatever your REST API endpoint supports/ expects.

Send as binary data

onUpload() {
  // this.http is the injected HttpClient
  this.http.post('my-backend.com/file-upload', this.selectedFile)
    .subscribe(...);
}

Send as FormData

onUpload() {
  // this.http is the injected HttpClient
  const uploadData = new FormData();
  uploadData.append('myFile', this.selectedFile, this.selectedFile.name);
  this.http.post('my-backend.com/file-upload', uploadData)
    .subscribe(...);
}

Listen to upload progress

In both cases, you can listen to the upload progress by editing the above code like this:

onUpload() {
  ...
  this.http.post('my-backend.com/file-upload', uploadData, {
    reportProgress: true,
    observe: 'events'
  })
    .subscribe(event => {
      console.log(event); // handle event here
    });
}

Make sure to watch the video above this article to see it all in action and to see the finished code.