Below code helped me getting my requirement.
var resultarray = [];
var a = $('#pageStyleCss').html();
if (a != undefined) {
while (a.indexOf('{') != -1) {
resultarray.push(a.substring(0, a.indexOf('{')));
a = a.substring(a.indexOf('}') + 1);
}
}
var i, option = "<option value=""></option>"
for (i = 0; i < resultarray.length; ++i) {
if (resultarray[i].indexOf('.') > -1) {
option += '<option value="' + resultarray[i].trim().replace('.', '') + '">' + resultarray[i].trim().replace('.', '') + '</option>';
}
}
solved Get css class list from style tag