[javascript] How to move all HTML element children to another parent using JavaScript?

This answer only really works if you don't need to do anything other than transferring the inner code (innerHTML) from one to the other:

// Define old parent
var oldParent = document.getElementById('old-parent');

// Define new parent
var newParent = document.getElementById('new-parent');

// Basically takes the inner code of the old, and places it into the new one
newParent.innerHTML = oldParent.innerHTML;

// Delete / Clear the innerHTML / code of the old Parent
oldParent.innerHTML = '';

Hope this helps!