sp15_nav.js

(function($){
	
    $(document).ready(function(){
    	
        var scriptBase = _spPageContextInfo.webAbsoluteUrl + "/_layouts/15/";	
    
    	$.getScript(scriptBase + "sp.runtime.js",function(){
    		
    		$.getScript(scriptBase + "sp.js",function(){
    			
    			$.getScript(scriptBase + "sp.publishing.js", modifyNavigation);
    			
    		});
    	});
    });
	
    function modifyNavigation(){
		
    	//Current Context
    	var context = SP.ClientContext.get_current();
    	
    	//Current Web
    	var currentWeb = context.get_web();		
		
        //Navigation Provider Settings for Current Web.
        var webNavSettings = new SP.Publishing.Navigation.WebNavigationSettings(context, currentWeb);
		
        //Current Navigation (Quick Launch)
        var navigation = webNavSettings.get_currentNavigation();
		
        //Global Navigation (Top Navigation Bar)
        //var navigation = webNavSettings.get_globalNavigation();

        /*
        unknown: 0, 
        portalProvider: 1 (Structural Navigation), 
        taxonomyProvider: 2 (You will need the Term Store Id and Term Set Id too),
        inheritFromParentWeb: 3 */
        navigation.set_source(1);
        
        webNavSettings.update();
        		
        context.executeQueryAsync(function(){
        
        	alert("Navigation Modification Successful");	
	
        },function(sender,args){
        	
        	alert(args.get_message());
		
        });

	
    }	

})(jQuery);