document.cookie not working in js for aem 6.3.2

function getCookie(cname) {

    var name = cname + "=";

    var ca = document.cookie.split(';');

    for(var i = 0; i < ca.length; i++) {

        var c = ca[i];

        while (c.charAt(0) == ' ') {

            c = c.substring(1);

        }

        if (c.indexOf(name) == 0) {

            return c.substring(name.length, c.length);

        }

    }

    return "";

Component is throwing "ReferenceError":Document is not defined error. How can we handle this?