SP.Navigation.quickLaunch property (sp.js)
Gets a value that collects navigation nodes corresponding to links in the Quick Launch area of the site.
Applies to: apps for SharePoint | SharePoint Foundation 2013 | SharePoint Server 2013
var value = SP.Navigation.get_quickLaunch ()
Return value
Type: SP.NavigationNodeCollection
Remarks
It must be null if the Quick Launch node is unavailable.