Let us discuss how to do file upload in Angular.js in this session.

Create an HTML template with input tag of input type as file. Create a function to event for handling choosing files.

<div class="form-group">
    <label for="file">Choose File</label>
    <input type="file"
           id="file"
           (change)="handleFileInput($event.target.files)">
</div>

Now set a default variable for selected file.

fileToUpload: File = null;

Create  a function to use in event of your file input tag.

handleFileInput(files: FileList) {
    this.fileToUpload = files.item(0);
}

If you want to use multiple file selection then repeat through files array. The file upload function ie. file -upload-service:

postFile(fileToUpload: File): Observable<boolean> {
    const endpoint = 'your-destination-url';
    const formData: FormData = new FormData();
    formData.append('fileKey', fileToUpload, fileToUpload.name);
    return this.httpClient
      .post(endpoint, formData, { headers: yourHeadersConfig })
      .map(() => { return true; })
      .catch((e) => this.handleError(e));
}

Calling  file upload service:

uploadFileToActivity() {
    this.fileUploadService.postFile(this.fileToUpload).subscribe(data => {
      // do something, if upload success
      }, error => {
        console.log(error);
      });
  }