if some image did not load sho alert javascript code example
Example 1: oneerror javascript image
<img src="imagenotfound.gif" alt="Image not found" onerror="this.onerror=null;this.src='imagefound.gif';" />
Example 2: js detect all images errors
window.addEventListener("error", e => {
/* query selector images */
// image element on error => replace source
})