An example of how to use eZ JS REST API to create a new content and get article user-friendly URL in the end.

createContent.js

var pageUrl     = 'http://ez.local',         
    authAgent   = new SessionAuthAgent({                 
        login   : 'admin',                 
        password: 'admin'         
    }),         
    jsRestClient        = new CAPI(pageUrl, authAgent),
    contentService      = jsRestClient.getContentTypeService(),
    parentLocationId    = '/api/ezp/v2/content/locations/1/2/102',
    contentTypeId       = '/api/ezp/v2/content/types/16',
    locationStruct      = contentService.newLocationStruct(parentLocationId),
    contentCreateStruct = contentService.newContentCreateStruct(contentTypeId, locationStruct, callback);

contentService.createContent(contentCreateStruct, function (error, response) {
    contentService.loadLocations(response.document.Content._href, function (error, response) {
        contentService.listLocationAliases(response.document.LocationList.Location[0]._href, false, function (error, response) {
            contentService.loadUrlAlias(response.document.UrlAliasRefList.UrlAlias[0]._href, function (error, response) {
                console.log(response.document.UrlAlias.path);
            });
        });
    });
});