This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The styleSheets read-only property of the DocumentOrShadowRoot interface returns a StyleSheetList of CSSStyleSheet objects, for stylesheets explicitly linked into or embedded in a document.
var styleSheetList = document.styleSheets;
The returned object is a StyleSheetList of CSSStyleSheet objects.
function getStyleSheet(unique_title) {
  for(var i=0; i<document.styleSheets.length; i++) {
    var sheet = document.styleSheets[i];
    if(sheet.title == unique_title) {
      return sheet;
    }
  }
}  The returned list is ordered as follows:
Link headers are placed first, sorted in header order.| Specification | Status | Comment | 
|---|---|---|
| Shadow DOM The definition of 'DocumentOrShadowRoot' in that specification.  |  Obsolete | Initial definition. | 
| Desktop | ||||||
|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | |
| Basic support | 53 | Yes | Yes | Yes | 40 | Yes | 
| Mobile | |||||||
|---|---|---|---|---|---|---|---|
| Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
| Basic support | 53 | 53 | Yes | Yes | 40 | Yes | 6.0 | 
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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/DocumentOrShadowRoot/styleSheets