Wrap an HTML structure around an element

How to use a given container as wrapper for another DOM element.

Wrap a given element in a new container element using plain JavaScript:

// element that will be wrapped
var el = document.querySelector('div.wrap_me');

// create wrapper container
var wrapper = document.createElement('div');

// insert wrapper before el in the DOM tree
el.parentNode.insertBefore(wrapper, el);

// move el into wrapper

The same procedure in form of a helper function:

function wrap(el, wrapper) {
el.parentNode.insertBefore(wrapper, el);

// example: wrapping an anchor with class "wrap_me" into a new div element
wrap(document.querySelector('a.wrap_me'), document.createElement('div'));

Functions to replace jQuery's $.wrap() and $.wrapAll() can be found on Stack Overflow.