You can use readCookie() function to read the cookie. It provides sufficient arguments that one can find it, flexible to use. It takes cookieName as a parameter and other statements in the block. Below function uses the cookie function as well as regular expression to show the functionality:

function readCookie(cookieName)

{ var rx = new RegExp('[; ]'+cookieName+'=([^s;]*)');

var sMatch = (' '+document.cookie).match(rx);

if (cookieName && sMatch) return unescape(sMatch[1]);

return '';

}