gistfile1.js

// Create scrollLeft and scrollTop methods
jQuery.each( ["Left", "Top"], function( isScrollTop, name ) {
	var method = "scroll" + name;

	jQuery.fn[ method ] = function( val ) {
		var elem, win;

		if( val === undefined ) {
			elem = this[ 0 ];
			if( !elem ) {
				return null;
			}

			win = getWindow( elem );
			// Return the scroll offset
			return !win ? elem[ method ] :
					("pageXOffset" in win) ? win[ isScrollTop ? "pageYOffset" : "pageXOffset" ] :
						jQuery.support.boxModel && win.document.documentElement[ method ] || win.document.body[ method ];
		}

		// Set the scroll offset
		return this.each(function() {
			win = getWindow( this );

			if ( win ) {
				win.scrollTo(
					!isScrollTop ? val : jQuery( win ).scrollLeft(),
					 isScrollTop ? val : jQuery( win ).scrollTop()
				);
			} else {
				this[ method ] = val;
			}
		});
	};
});

gistfile2.diff

diff --git a/src/offset.js b/src/offset.js
index 8696c20..7a235a9 100644
--- a/src/offset.js
+++ b/src/offset.js
@@ -257,7 +257,7 @@ jQuery.fn.extend({
 
 
 // Create scrollLeft and scrollTop methods
-jQuery.each( ["Left", "Top"], function( i, name ) {
+jQuery.each( ["Left", "Top"], function( isScrollTop, name ) {
        var method = "scroll" + name;
 
        jQuery.fn[ method ] = function( val ) {
@@ -271,10 +271,9 @@ jQuery.each( ["Left", "Top"], function( i, name ) {
 
                        win = getWindow( elem );
                        // Return the scroll offset
-                       return win ? ("pageXOffset" in win) ? win[ i ? "pageYOffset" : "pageXOffset" ] :
-                               jQuery.support.boxModel && win.document.documentElement[ method ] ||
-                                       win.document.body[ method ] :
-                               elem[ method ];
+                       return !win ? elem[ method ] :
+                                       ("pageXOffset" in win) ? win[ isScrollTop ? "pageYOffset" : "pageXOffset" ] :
+                                               jQuery.support.boxModel && win.document.documentElement[ method ] || win
                }
 
                // Set the scroll offset
@@ -283,8 +282,8 @@ jQuery.each( ["Left", "Top"], function( i, name ) {
 
                        if ( win ) {
                                win.scrollTo(
-                                       !i ? val : jQuery( win ).scrollLeft(),
-                                        i ? val : jQuery( win ).scrollTop()
+                                       !isScrollTop ? val : jQuery( win ).scrollLeft(),
+                                        isScrollTop ? val : jQuery( win ).scrollTop()
                                );
                        } else {
                                this[ method ] = val;

Link to current scrollTop/Left method: https://github.com/jquery/jquery/blob/master/src/offset.js#L259-295