multiple file upload with angular reactive forms

Question

I am trying to build a form in Angular 6 that offers a file selection box that allows the user to select multiple files (Stackblitz: https://stackblitz.com/edit/angular-yjummp).

The Template looks like:

<form [formGroup]="form">
    <input id="files" formControlName="files" type="file" accept="image/*,video/*" multiple (change)="onFilesChanged($event)"/>
</form>

I am building the form in TypeScript like this:

  public form = new FormGroup({
    files: new FormControl('')
  });

  public onFilesChanged(event: any): void {
    console.log(event.target.files);
    console.log(this.form.value);
  }

Now, in the onFilesChanged Handler, the selected files can be correctly retrieved from the event by accessing event.target.files (obviously), but printing the form value only prints one file. I have been trying a number of ways using FormArray as well, but had no luck so far.

Any ideas? Many thanks!

Answer 1

Below is example that how I achieved multiple photo upload input file through angular reactive forms.

public demoForm: FormGroup;

constructor(private formBuilder: FormBuilder) { 
    this.demoForm = this.formBuilder.group({
       text_input: ['', Validators.required],
       photos: this.formBuilder.array([])
    });
}

// We will create multiple form controls inside defined form controls photos.
createItem(data): FormGroup {
    return this.formBuilder.group(data);
}

//Help to get all photos controls as form array.
get photos(): FormArray {
    return this.demoForm.get('photos') as FormArray;
};

detectFiles(event) {
    let files = event.target.files;
    if (files) {
        for (let file of files) {
            let reader = new FileReader();
            reader.onload = (e: any) => {
                this.photos.push(this.createItem({
                    file,
                    url: e.target.result  //Base64 string for preview image
                }));
            }
            reader.readAsDataURL(file);
        }
    }
}

In component html

<input type="file" class="custom-file-input form-control" id="files" multiple (change)="detectFiles($event)" accept="image/x-png,image/jpeg">

<div class="images-preview mt-2" *ngIf="photos.length">
    <div formArrayName="photos" *ngFor="let photo of photos.controls; let i = index;">
        <div [formGroupName]="i">
            <img [src]="photo.controls.url.value" class="card-img-top" alt="Image Preview">
        </div>
    </div>
</div>

You can avoid html if you do not want to show preview. On submit of form you will be get values like below.

{
    text_input: "",
    photos: [
       {
           file: <File Object>,
           url: <Base64 String here>
       },
       {
           file: <File Object>,
           url: <Base64 String here>
       },
       ....
    ] 
}

Edit Here is working stackblitz example

I hope it will helps you and also other peoples. Thanks.