filebrowser/_assets/src/utils/css.js

export default function getRule (rules) {
  for (let i = 0; i < rules.length; i++) {
    rules[i] = rules[i].toLowerCase()
  }

  let result = null
  let find = Array.prototype.find

  find.call(document.styleSheets, styleSheet => {
    result = find.call(styleSheet.cssRules, cssRule => {
      let found = false

      if (cssRule instanceof window.CSSStyleRule) {
        for (let i = 0; i < rules.length; i++) {
          if (cssRule.selectorText.toLowerCase() === rules[i]) {
            found = true
          }
        }
      }

      return found
    })

    return result != null
  })

  return result
}