Ionic-native file

Hi. I’m sure I’m a newbie at IONIC

I need to know if an image exists in a directory of the APP, and in case there is no display an image from url.

I am using

@ ionic-native / file

In the .ts I put the following

Import {File} from '@ ionic-native / file';

In the constructor I put

Private file: File,

Then I have the following function

This.file.checkDir (this.file.dataDirectory, 'assets / img / header_home.jpg')
.then (_ => console.log ('Directory exists'))
.catch (err => console.log ('Directory doesnt exist'));

What I do not understand is how to save the image url in a variable and then display it in the HTML