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.
DocumentType: before() method
Syntax
js
before(param1)
before(param1, param2)
before(param1, param2, /* …, */ paramN)
Parameters
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:
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