web api instance method
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
before(param1)
before(param1, param2)
before(param1, param2, /* …, */ paramN)
Parameters
param1, …,paramN- : A set of
Nodeobjects or strings to insert.
- : A set of
Return value
None (undefined).
Exceptions
HierarchyRequestErrorDOMException- : 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:
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
SpecificationsStandards references are available on the canonical MDN page.
Browser compatibility
Browser compatibilityCompatibility data is available on the canonical MDN page.