document.evaluate - 跨浏览器？

function SparkEn(xpath,root) {
  xpath = xpath
    .replace(/((^||)s*)([^/|s]+)/g,'$2.//$3')
    .replace(/.([w-]+)(?!([^]]*]))/g, '[@class="$1" or @class$=" $1" or @class^="$1 " or @class~=" $1 "]')
    .replace(/#([w-]+)/g, '[@id="$1"]')
    .replace(//[/g,'/*[');
  str = '(@\w+|"[^"]*"|'[^']*')';
  xpath = xpath
    .replace(new RegExp(str+'\s*~=\s*'+str,'g'), 'contains($1,$2)')
    .replace(new RegExp(str+'\s*\^=\s*'+str,'g'), 'starts-with($1,$2)')
    .replace(new RegExp(str+'\s*\$=\s*'+str,'g'), 'substring($1,string-length($1)-string-length($2)+1)=$2');
  var got = document.evaluate(xpath, root||document, null, 5, null);
  var result=[];
  while (next = got.iterateNext())
    result.push(next);
  return result;
}