If there is no picture, how to take it from another host?

Question

JavaScript

If there is no image on host1, display it on the page from host2.
Including subfolders etc.
You need to play around with a copy of the site in the sandbox, and the pictures there between the files will only interfere.
PS: Well, or in general, all the pictures on the mask.
PPP: Well, or another method, mb JS? (just not inline to every link)

Answer 1

;(function(){
  [].slice.call(document.querySelectorAll('img'))
    .forEach(img=>img.addEventListener('error', evt=>{
    img.src = img.src.replace(
      'https://fiddle.jshell.net/badpath/',
      'https://i.imgur.com/'
    )
  }))
})()

UPD : It turns out that the img.onerror event does not pop up, so you have to hang a handler on every img tag.
Working example: https://jsfiddle.net/Stalk/j3q47rco/