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DocumentType: before() method

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 Standard
# ref-for-dom-childnode-before①

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
before 54 17 49 No 39 10 54 54 49 41 10 6.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/DocumentType/before