Scroll to numeric position, DOM element, jQuery object, or jQuery selector

scrollto.js

/**
* @author Zakir Tariverdiev
* @description jQuery scroll utility method alllowing animated scrolling 
* to the specified entity.
* Chckout example http://jsfiddle.net/zakirt/hsb2v9ju/
* @param {number|string|Element|jQuery} - numeric position, 
* jQuery selector string, DOM element, or jQuery object to scroll to.
* @returns promise object
*/
 
(function($) {
    'use strict';
    
    // Avoid possible conflicts with identically named jQuery method
    if (typeof $.scrollTo === 'undefined') {
 
        $.scrollTo = function(where, animDuration) {
            var scrollPos = null;
                
            if (typeof where !== 'undefined') {
                
                // Numeric offset?
                if (typeof where === 'number') {
                    scrollPos = where; 
                }
                // String selector, or numeric value as string?
                else if (typeof where === 'string') { 
                    
                    if (!isNaN(parseInt(where, 10))) {
                        scrollPos = parseInt(where, 10);            
                    }                
                    else if ($(where).length !== 0) {
                        scrollPos = $(where).offset().top;
                    }       
                }
                // DOM element?
                else if (typeof where.nodeType !== 'undefined' && where.nodeType === Node.ELEMENT_NODE) {
                    scrollPos = $(where).offset().top;
                }
                // jQuery instance
                else if (where instanceof jQuery) {
                    scrollPos = where.offset().top;
                }
            }
           
            // All went smoothly and we have a valid offset value
            if (scrollPos !== null) {      
                var duration = animDuration || 600;
            
                return $('body,html').animate({
                    scrollTop: scrollPos
                }, duration).promise();
            }
        };
    }
})(jQuery);