Using a default image on load of the page, then overwrites it

I have a page wich contains several images. When the page loads it provides a default image for each IMG:

import default from './pics/default.jpg';

<img src={default} alt="#"/>

What I want is something like this:

<img src1={default} src2="img url" alt="#"/>

Where src2 overwrites src1 when it is loaded.

Edit: The first image (src1) comes as the page loads while the second (src2) is requested trough the internet. Example: https://cdn.pixabay.com/photo/2016/10/17/10/52/wind-farm-1747331__340.jpg

from Using a default image on load of the page, then overwrites it