這個polyfill如何爲document.queryselectorall工作？

Question

我想了解queryselectorall的這個polyfill？ Specifially這一行：

styleTag.styleSheet.cssText = selector + "{x:expression(document.__qsaels.push(this))}"; 

https://gist.github.com/connrs/2724353

if (!document.querySelectorAll) { 
    document.querySelectorAll = function(selector) { 
     var doc = document, 
      head = doc.documentElement.firstChild, 
      styleTag = doc.createElement('STYLE'); 
     head.appendChild(styleTag); 
     doc.__qsaels = []; 

     styleTag.styleSheet.cssText = selector + "{x:expression(document.__qsaels.push(this))}"; 
     window.scrollBy(0, 0); 

     return doc.__qsaels; 
    } 
} 

Answer 1

據濫用CSS的expression "feature"。在計算x屬性的風格（發生在由scrollBy(0, 0)觸發的迴流時）時，Internet Explorer將爲與選擇器匹配的所有元素執行此代碼段。

CSS expressions are officially despised因爲IE 8 ...