Change background image with button

background.css

#imgDiv {
  width: 400px;
  height: 400px;
  background-image: url('http://placehold.it/400.png&text=New_Image/464545/e743c3');
}

changeBackground.html

<div>
  <button onClick="myFunction()">Change Background</button>
</div>

newBackground.js

function myFunction() {
  document.getElementById("imgDiv").style.backgroundImage = "url(http://placehold.it/400.png&text=New_Image/464545/e743c3)";
}