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Node: compareDocumentPosition() method

The compareDocumentPosition() method of the Node interface reports the position of its argument node relative to the node on which it is called.

Syntax

compareDocumentPosition(otherNode)

Parameters

otherNode: The Node for which position should be reported, relative to the node.

Return value

An integer value representing otherNode's position relative to node as a bitmask combining the following constant properties of Node:

Node.DOCUMENT_POSITION_DISCONNECTED (1): Both nodes are in different documents or different trees in the same document.
Node.DOCUMENT_POSITION_PRECEDING (2): otherNode precedes the node in either a pre-order depth-first traversal of a tree containing both (e.g., as an ancestor or previous sibling or a descendant of a previous sibling or previous sibling of an ancestor) or (if they are disconnected) in an arbitrary but consistent ordering.
Node.DOCUMENT_POSITION_FOLLOWING (4): otherNode follows the node in either a pre-order depth-first traversal of a tree containing both (e.g., as a descendant or following sibling or a descendant of a following sibling or following sibling of an ancestor) or (if they are disconnected) in an arbitrary but consistent ordering.
Node.DOCUMENT_POSITION_CONTAINS (8): otherNode is an ancestor of the node.
Node.DOCUMENT_POSITION_CONTAINED_BY (16): otherNode is a descendant of the node.
Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC (32): The result relies upon arbitrary and/or implementation-specific behavior and is not guaranteed to be portable.

More than one bit is set if multiple scenarios apply. For example, if otherNode is located earlier in the document and contains the node on which compareDocumentPosition() was called, then both the DOCUMENT_POSITION_CONTAINS and DOCUMENT_POSITION_PRECEDING bits would be set, producing a value of 10 (0x0A).

Example

const head = document.head;
const body = document.body;

if (head.compareDocumentPosition(body) & Node.DOCUMENT_POSITION_FOLLOWING) {
  console.log("Well-formed document");
} else {
  console.error("<head> is not before <body>");
}

Note: Because the result returned by compareDocumentPosition() is a bitmask, the bitwise AND operator must be used for meaningful results.

Specifications

Specification
DOM Standard # ref-for-dom-node-comparedocumentposition①

Browser compatibility