Tips for storing an image in local storage with an angular reactive form

Question

Tips for storing an image in local storage with an angular reactive form

I'm currently working on an Angular project where my goal is to implement a feature that allows users to upload an image using an angular reactive form and then store that image in the local storage.

Here is a snippet of the code from "edit.component.html" file:

<form [formGroup]="form" (ngSubmit)="save()">
<label class="head1">Photo</label> <br>
<input type="file" formControlName="Photo">
<button [disabled]="form.invalid">Save</button>
</form>

And here is a glimpse of the code inside "edit.component.ts":

import { Component } from '@angular/core';
import { FormGroup, FormControl, Validators, FormArray} from '@angular/forms';

@Component({
  selector: 'app-edit',
  templateUrl: './edit.component.html',
  styleUrls: ['./edit.component.css']
})
export class EditComponent {
form=new FormGroup({
    Photo:new FormControl(null,Validators.required),
});
save(){
    var profile;

    if(localStorage.getItem("profile")==null){
      profile={};
    }
    else{
      profile=JSON.parse(localStorage.getItem("profile")!);
    }

    // Need help with saving the image to localstorage
}
}

Upon adding the line

const photo = this.form.get('Photo') as File;

in the save() function of ts file, I encountered the following error:

Conversion of type 'AbstractControl<null, null> | null' to type 'File' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type 'AbstractControl<null, null>' is missing the following properties from type 'File': lastModified, name, webkitRelativePath, size, and 6 more.ts(2352)

Could someone please offer guidance or suggest modifications to successfully save the image in localstorage and display it on the HTML page?

angular typescript image forms angular-reactive-forms

Answer 1

Answer №1

To convert an image into a string, you can use the FileReader method as local storage works with strings. You can then save this converted string.

Afterwards, you have the option to retrieve the string from local storage and convert it back into a file using the File method, adding it back to the form.

You can set up a listener for changes in the file field, which will capture the file, assign it to the form, and save it accordingly.

If you'd like to see a demonstration of this process, check out this Stackblitz example.

Feel free to customize these methods based on your specific requirements.

Key methods:

File Handler:

<input
    type="file"
    formControlName="Photo"
    (change)="handleFileInput($event)"
  />

handleFileInput(event: Event) {
    const target = event.target as HTMLInputElement;

    const files = target.files as FileList;

    const file = files[0];

    this.form.value.Photo = file;

    this.saveFile(file);
}

Save File:

saveFile(file: File) {
    const reader = new FileReader();

    reader.onloadend = () => {
      console.log(reader.result);

      this.preview = reader.result as string;

      localStorage.setItem('profile', reader.result as string);
    };
    reader.readAsDataURL(file);
}

Read File:

readFile() {
    const profile = localStorage.getItem('profile');

    console.log('reading ls image: ', profile);

    if (profile) {
      this.preview = profile;

      const contentType = profile.split(';')[0].replace('data:', '');

      const file = new File([profile], 'profile.jpeg', {
        type: contentType,
      });

      this.form.value.Photo = file;
    } else {
      this.preview = '';
    }
}

Answer 2

To convert an image into a string, you can use the FileReader method as local storage works with strings. You can then save this converted string.

Afterwards, you have the option to retrieve the string from local storage and convert it back into a file using the File method, adding it back to the form.

You can set up a listener for changes in the file field, which will capture the file, assign it to the form, and save it accordingly.

If you'd like to see a demonstration of this process, check out this Stackblitz example.

Feel free to customize these methods based on your specific requirements.

Key methods:

File Handler:

<input
    type="file"
    formControlName="Photo"
    (change)="handleFileInput($event)"
  />

handleFileInput(event: Event) {
    const target = event.target as HTMLInputElement;

    const files = target.files as FileList;

    const file = files[0];

    this.form.value.Photo = file;

    this.saveFile(file);
}

Save File:

saveFile(file: File) {
    const reader = new FileReader();

    reader.onloadend = () => {
      console.log(reader.result);

      this.preview = reader.result as string;

      localStorage.setItem('profile', reader.result as string);
    };
    reader.readAsDataURL(file);
}

Read File:

readFile() {
    const profile = localStorage.getItem('profile');

    console.log('reading ls image: ', profile);

    if (profile) {
      this.preview = profile;

      const contentType = profile.split(';')[0].replace('data:', '');

      const file = new File([profile], 'profile.jpeg', {
        type: contentType,
      });

      this.form.value.Photo = file;
    } else {
      this.preview = '';
    }
}

Tips for storing an image in local storage with an angular reactive form

Answer №1

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