This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The read-only systemId property of the DocumentType returns the URL of the associated DTD.
For synthetic DocumentType, this property reflects the value given in parameter to DOMImplementation.createDocumentType().
A string.
const docType = document.implementation.createDocumentType( "svg", "", "http://www.w3.org/2000/svg", ); console.log(docType.systemId); // Displays "http://www.w3.org/2000/svg"
| Specification |
|---|
| DOM> # dom-documenttype-systemid> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
systemId |
1 | 12 | 1 | ≤12.1 | 3 | 18 | 4 | ≤12.1 | 1 | 1.0 | 4.4 | 1 |
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https://developer.mozilla.org/en-US/docs/Web/API/DocumentType/systemId