A small snippet to select element sin JavaScript using CSS selector syntax.

selector

function $$(xpath,root) { 
 2   xpath = xpath
 3     .replace(/((^|\|)\s*)([^/|\s]+)/g,'$2.//$3')
 4     .replace(/\.([\w-]+)(?!([^\]]*]))/g, '[@class="$1" or @class$=" $1" or @class^="$1 " or @class~=" $1 "]')
 5     .replace(/#([\w-]+)/g, '[@id="$1"]')
 6     .replace(/\/\[/g,'/*[');
 7   str = '(@\\w+|"[^"]*"|\'[^\']*\')';
 8   xpath = xpath
 9     .replace(new RegExp(str+'\\s*~=\\s*'+str,'g'), 'contains($1,$2)')
10     .replace(new RegExp(str+'\\s*\\^=\\s*'+str,'g'), 'starts-with($1,$2)')
11     .replace(new RegExp(str+'\\s*\\$=\\s*'+str,'g'), 'substring($1,string-length($1)-string-length($2)+1)=$2');
12   var got = document.evaluate(xpath, root||document, null, 5, null);
13   var result=[];
14   while (next = got.iterateNext())
15     result.push(next);
16   return result;
17 }
18 
19 
20 
21 // Example usage:
22 
23 $$('#title')[0].innerHTML='Greased';
24 
25 $$('a[@href $= "user.js"]').forEach(function (a) {
26   a.innerHTML='check it out a script';
27 });
28 
29 $$('a[@href ^= "http"]').forEach(function (a) {
30   a.innerHTML += ' (external)';
31 });