DocumentType: before() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The DocumentType.before() method inserts a set of Node objects or strings in the children list of the DocumentType's parent, just before the DocumentType. Strings are inserted as equivalent Text nodes.

Syntax

js
before(param1)
before(param1, param2)
before(param1, param2, /* …, */ paramN)

Parameters

param1, …, paramN

A set of Node objects or strings to insert.

Return value

None (undefined).

Exceptions

HierarchyRequestError DOMException

Thrown when the node cannot be inserted at the specified point in the hierarchy.

Examples

Adding a conditional comment

Comment nodes are valid before doctype declarations but not advisable given they trigger quirks mode in IE. A conditional comment works for IE as well, though:

js
let docType = document.implementation.createDocumentType("html", "", "");
let myDoc = document.implementation.createDocument("", "", docType);

docType.before(
  document.createComment("<!--[if !IE]> conditional comment <![endif]-->"),
);

myDoc.childNodes;
// NodeList [<!--[if !IE]> conditional comment <![endif]-->, <!DOCTYPE html>]

Specifications

Specification
DOM
# ref-for-dom-childnode-before①

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
before

Legend

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Full support
Full support

See also