提取页面上用到的所有CSS

var result = [];
[].forEach.call(document.styleSheets, function(item1) {
  debugger
  if (item1.cssRules) {
    [].forEach.call(item1.cssRules, function(item2) {
      var sign = false
      if (!item2.selectorText) sign = false
      else if (document.querySelector(item2.selectorText)) sign = true
      else {
        var str = String(item2.selectorText).replace(/\:+[^:\,]*/ig, '')
        try { if (document.querySelector(str)) sign = true } catch (e) {console.log(e)}
        var list = str.split(',')
        list.forEach(function (item3) {
          try { if (document.querySelector(item3)) sign = true } catch (e) {console.log(e)}
        })
      }
      if (sign) result.push(item2.cssText)
    })
  } else {
    console.log('[crossorigin]: ' + item1.href)
  }
});
result;
var out = document.getElementById('out')
if (!out) {
  document.body.insertAdjacentHTML('afterEnd', '
123')
  out = document.getElementById('out')
}
out.innerHTML = result.join('')

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