add tests and support markup

3 files changed, 36 insertions, 7 deletions

diff --git a/js/src/scrollspy.js b/js/src/scrollspy.js
index 83080e800f..f4d6671013 100644
--- a/js/src/scrollspy.js
+++ b/js/src/scrollspy.js
@@ -112,6 +112,13 @@ class ScrollSpy extends BaseComponent {
     // TODO: on v6 target should be given explicitly & remove the {target: 'ss-target'} case
     config.target = getElement(config.target) || document.body
 
+    // TODO: v6 Only for backwards compatibility reasons. Use rootMargin only
+    config.rootMargin = config.offset ? `${config.offset}px 0px -30%` : config.rootMargin
+
+    if (typeof config.threshold === 'string') {
+      config.threshold = config.threshold.split(',').map(value => Number.parseFloat(value))
+    }
+
     return config
   }
 
@@ -144,7 +151,7 @@ class ScrollSpy extends BaseComponent {
     const options = {
       root: this._rootElement,
       threshold: this._config.threshold,
-      rootMargin: this._getRootMargin()
+      rootMargin: this._config.rootMargin
     }
 
     return new IntersectionObserver(entries => this._observerCallback(entries), options)
@@ -189,11 +196,6 @@ class ScrollSpy extends BaseComponent {
     }
   }
 
-  // TODO: v6 Only for backwards compatibility reasons. Use rootMargin only
-  _getRootMargin() {
-    return this._config.offset ? `${this._config.offset}px 0px -30%` : this._config.rootMargin
-  }
-
   _initializeTargetsAndObservables() {
     this._targetLinks = new Map()
     this._observableSections = new Map()
diff --git a/js/tests/unit/scrollspy.spec.js b/js/tests/unit/scrollspy.spec.js
index 61edeb921a..b1c8053033 100644
--- a/js/tests/unit/scrollspy.spec.js
+++ b/js/tests/unit/scrollspy.spec.js
@@ -132,7 +132,7 @@ describe('ScrollSpy', () => {
         '   <a class="nav-link active" id="one-link" href="#">One</a>' +
         '</ul>',
         '<div id="content">',
-        '  <div id="one-link" style="height: 300px;">test</div>',
+        '  <div id="one-link">test</div>',
         '</div>'
       ].join('')
 
@@ -144,6 +144,31 @@ describe('ScrollSpy', () => {
       expect(scrollSpy._observer.thresholds).toEqual([1])
     })
 
+    it('should respect threshold option mark-up', () => {
+      fixtureEl.innerHTML = [
+        '<ul id="navigation" class="navbar">',
+        '   <a class="nav-link active" id="one-link" href="#">One</a>' +
+        '</ul>',
+        '<div id="content" data-bs-threshold="0,0.2,1">',
+        '  <div id="one-link">test</div>',
+        '</div>'
+      ].join('')
+
+      const scrollSpy = new ScrollSpy('#content', {
+        target: '#navigation'
+      })
+
+      const expectToBeCloseToArray = (actual, expected) => {
+        expect(actual.length).toBe(expected.length)
+        for (const x of actual) {
+          const i = actual.indexOf(x)
+          expect(x).withContext(`[${i}]`).toBeCloseTo(expected[i])
+        }
+      }
+
+      expectToBeCloseToArray(scrollSpy._observer.thresholds, [0, 0.2, 1])
+    })
+
     it('should not take count to not visible sections', () => {
       fixtureEl.innerHTML = [
         '<nav id="navigation" class="navbar">',
diff --git a/site/content/docs/5.2/components/scrollspy.md b/site/content/docs/5.2/components/scrollspy.md
index 5e329dc85a..9b8b761d69 100644
--- a/site/content/docs/5.2/components/scrollspy.md
+++ b/site/content/docs/5.2/components/scrollspy.md
@@ -380,6 +380,8 @@ const scrollSpy = new bootstrap.ScrollSpy(document.body, {
 | `rootMargin` | string | `0px 0px -40%` | Intersection Observer [rootMargin](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/rootMargin) valid units, when calculating scroll position. |
 | `smoothScroll` | boolean | `false` | Enables smooth scrolling when a user clicks on a link that refers to ScrollSpy observables. |
 | `target` | string \| jQuery object \| DOM element |  | Specifies element to apply Scrollspy plugin. |
+| `threshold` | array | `[0.1, 0.5, 1]` | Intersection Observer [threshold](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver#threshold) valid input, when calculating scroll position.|
+
 {{< /bs-table >}}
 
 {{< callout warning >}}