/*

possible values:

​

Node.DOCUMENT_POSITION_DISCONNECTED: 1

Node.DOCUMENT_POSITION_PRECEDING: 2

Node.DOCUMENT_POSITION_FOLLOWING: 4

Node.DOCUMENT_POSITION_CONTAINS: 8

Node.DOCUMENT_POSITION_CONTAINED_BY: 16

Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC: 32

*/

​

var one = document.getElementById('one'),

    two = document.getElementById('two'),

    head = document.getElementsByTagName('head')[0],

    body = document.getElementsByTagName('body')[0];

​

if (one.compareDocumentPosition(two) === 20) {

  console.log('one contains two');

}

​

if (head.compareDocumentPosition(body) === 4) {

  console.log('head precedes body');

}

​

​