address https://github.com/twbs/bootstrap/pull/16135

js/dist/scrollspy.js

@@ -27,7 +27,8 @@ var ScrollSpy = (function ($) {
   var JQUERY_NO_CONFLICT = $.fn[NAME];
 
   var Default = {
-    offset: 10
+    offset: 10,
+    method: 'auto'
   };
 
   var Event = {
@@ -48,6 +49,11 @@ var ScrollSpy = (function ($) {
     LI: 'li'
   };
 
+  var OffsetMethod = {
+    OFFSET: 'offset',
+    POSITION: 'position'
+  };
+
   /**
    * ------------------------------------------------------------------------
    * Class Definition
@@ -81,13 +87,11 @@ var ScrollSpy = (function ($) {
       value: function refresh() {
         var _this = this;
 
-        var offsetMethod = 'offset';
-        var offsetBase = 0;
+        var autoMethod = this._scrollElement !== this._scrollElement.window ? OffsetMethod.POSITION : OffsetMethod.OFFSET;
 
-        if (this._scrollElement !== this._scrollElement.window) {
-          offsetMethod = 'position';
-          offsetBase = this._getScrollTop();
-        }
+        var offsetMethod = this._config.method === 'auto' ? autoMethod : this._config.method;
+
+        var offsetBase = offsetMethod === OffsetMethod.POSITION ? this._getScrollTop() : 0;
 
         this._offsets = [];
         this._targets = [];

js/src/scrollspy.js

@@ -25,7 +25,8 @@ const ScrollSpy = (($) => {
   const JQUERY_NO_CONFLICT = $.fn[NAME]
 
   const Default = {
-    offset : 10
+    offset : 10,
+    method : 'auto'
   }
 
   const Event = {
@@ -46,6 +47,11 @@ const ScrollSpy = (($) => {
     LI          : 'li'
   }
 
+  const OffsetMethod = {
+    OFFSET   : 'offset',
+    POSITION : 'position'
+  }
+
 
   /**
    * ------------------------------------------------------------------------
@@ -86,13 +92,14 @@ const ScrollSpy = (($) => {
     // public
 
     refresh() {
-      let offsetMethod = 'offset'
-      let offsetBase   = 0
+      let autoMethod = this._scrollElement !== this._scrollElement.window ?
+        OffsetMethod.POSITION : OffsetMethod.OFFSET
 
-      if (this._scrollElement !== this._scrollElement.window) {
-        offsetMethod = 'position'
-        offsetBase   = this._getScrollTop()
-      }
+      let offsetMethod = this._config.method === 'auto' ?
+        autoMethod : this._config.method
+
+      let offsetBase = offsetMethod === OffsetMethod.POSITION ?
+        this._getScrollTop() : 0
 
       this._offsets = []
       this._targets = []

js/tests/unit/scrollspy.js

@@ -275,4 +275,90 @@ $(function () {
       .then(function () { return testElementIsActiveAfterScroll('#li-100-1', '#div-100-1') })
   })
 
+  QUnit.test('should allow passed in option offset method: offset', function (assert) {
+      assert.expect(4)
+
+      var testOffsetMethod = function (type) {
+        var deferred = $.Deferred()
+        var navbarHtml =
+            '<nav class="navbar"' + (type === 'data' ? ' id="navbar-offset-method-menu"' : '') + '>'
+          + '<ul class="nav">'
+          + '<li id="li-' + type + 'm-1"><a href="#div-' + type + 'm-1">div 1</a></li>'
+          + '<li id="li-' + type + 'm-2"><a href="#div-' + type + 'm-2">div 2</a></li>'
+          + '<li id="li-' + type + 'm-3"><a href="#div-' + type + 'm-3">div 3</a></li>'
+          + '</ul>'
+          + '</nav>'
+        var contentHtml =
+            '<div class="content"' + (type === 'data' ? ' data-spy="scroll" data-target="#navbar-offset-method-menu" data-offset="0" data-method="offset"' : '') + ' style="position: relative; overflow: auto; height: 100px">'
+          + '<div id="div-' + type + 'm-1" style="position: relative; height: 200px; padding: 0; margin: 0">div 1</div>'
+          + '<div id="div-' + type + 'm-2" style="position: relative; height: 150px; padding: 0; margin: 0">div 2</div>'
+          + '<div id="div-' + type + 'm-3" style="position: relative; height: 250px; padding: 0; margin: 0">div 3</div>'
+          + '</div>'
+
+
+        $(navbarHtml).appendTo('#qunit-fixture')
+        var $content = $(contentHtml)
+          .appendTo('#qunit-fixture')
+
+        if (type === 'js') $content.bootstrapScrollspy({ target: '.navbar', offset: 0, method: 'offset' })
+        else if (type === 'data') $(window).trigger('load.bs.scrollspy.data-api')
+
+        var $target = $('#div-' + type + 'm-2')
+        var scrollspy = $content.data('bs.scrollspy')
+
+        assert.ok(scrollspy._offsets[1] === $target.offset().top, 'offsed method with ' + type + ' option')
+        assert.ok(scrollspy._offsets[1] !== $target.position().top, 'position method with ' + type + ' option')
+
+        deferred.resolve()
+
+        return deferred.promise()
+      }
+
+      $.when(testOffsetMethod('js'))
+        .then(function () { testOffsetMethod('data') })
+    })
+
+    QUnit.test('should allow passed in option offset method: position', function (assert) {
+      assert.expect(4)
+
+      var testOffsetMethod = function (type) {
+        var deferred = $.Deferred()
+        var navbarHtml =
+            '<nav class="navbar"' + (type === 'data' ? ' id="navbar-offset-method-menu"' : '') + '>'
+          + '<ul class="nav">'
+          + '<li id="li-' + type + 'm-1"><a href="#div-' + type + 'm-1">div 1</a></li>'
+          + '<li id="li-' + type + 'm-2"><a href="#div-' + type + 'm-2">div 2</a></li>'
+          + '<li id="li-' + type + 'm-3"><a href="#div-' + type + 'm-3">div 3</a></li>'
+          + '</ul>'
+          + '</nav>'
+        var contentHtml =
+            '<div class="content"' + (type === 'data' ? ' data-spy="scroll" data-target="#navbar-offset-method-menu" data-offset="0" data-method="position"' : '') + ' style="position: relative; overflow: auto; height: 100px">'
+          + '<div id="div-' + type + 'm-1" style="position: relative; height: 200px; padding: 0; margin: 0">div 1</div>'
+          + '<div id="div-' + type + 'm-2" style="position: relative; height: 150px; padding: 0; margin: 0">div 2</div>'
+          + '<div id="div-' + type + 'm-3" style="position: relative; height: 250px; padding: 0; margin: 0">div 3</div>'
+          + '</div>'
+
+
+        $(navbarHtml).appendTo('#qunit-fixture')
+        var $content = $(contentHtml)
+          .appendTo('#qunit-fixture')
+
+        if (type === 'js') $content.bootstrapScrollspy({ target: '.navbar', offset: 0, method: 'position' })
+        else if (type === 'data') $(window).trigger('load.bs.scrollspy.data-api')
+
+        var $target = $('#div-' + type + 'm-2')
+        var scrollspy = $content.data('bs.scrollspy')
+
+        assert.ok(scrollspy._offsets[1] !== $target.offset().top, 'offsed method with ' + type + ' option')
+        assert.ok(scrollspy._offsets[1] === $target.position().top, 'position method with ' + type + ' option')
+
+        deferred.resolve()
+
+        return deferred.promise()
+      }
+
+      $.when(testOffsetMethod('js'))
+        .then(function () { testOffsetMethod('data') })
+    })
+
 })