JS: Get base URL with level-back feature

At many times we need to extract the root of a multi-level path URL. So here is the code to do that.

/*
 @author Abhishek Kumar
 @usage getBaseUrl(n); where n = number of ../
 @example 
   For URL → http://localhost/workshop/showcase/shell/data/AKI/app/index.html
   Result of
     getBaseUrl() → http://localhost/workshop/showcase/shell/data/AKI/app/
     getBaseUrl(3) → http://localhost/workshop/showcase/shell/
*/
function getBaseUrl(levelback) {
    var basePath = window.location.pathname;
    basePath = basePath.substring(0, basePath.lastIndexOf('/'));
    var list = basePath.split('/');
    for (var i = 0; i < levelback && list.length > 0; i++) {
        list.pop();
    }
    return window.location.protocol + '//' + window.location.host + list.join('/') + '/';
}