Reveal photos on scroll on Location page

src/routes/[country]/[location]/index.svelte

@@ -27,7 +27,10 @@
     const hasIllustration = location.illustration_desktop && location.illustration_desktop_2x && location.illustration_mobile
 
     let introEl: HTMLElement
+    let photosListEl: HTMLElement
     let scrollY: number
+    let observerPhotos: IntersectionObserver
+    let mutationPhotos: MutationObserver
     let currentPage = 1
     let ended: boolean
     let currentPhotosAmount: number
@@ -138,6 +141,45 @@
             translateY: ['10%', 0],
             opacity: [0, 1],
         }, 900 + ($navigating ? DURATION.PAGE_IN : 0))
+
+
+        // Photos IntersectionObserver
+        observerPhotos = new IntersectionObserver(entries => {
+            entries.forEach(({ isIntersecting, target }: IntersectionObserverEntry) => {
+                target.classList.toggle('is-visible', isIntersecting)
+
+                // Run effect once
+                isIntersecting && observerPhotos.unobserve(target)
+            })
+        }, {
+            threshold: 0.3,
+            rootMargin: '0px 0px 0px'
+        })
+
+        // Photos MutationObserver
+        mutationPhotos = new MutationObserver((mutationsList, observer) => {
+            // When adding new childs
+            for (const mutation of mutationsList) {
+                if (mutation.type === 'childList') {
+                    // Observe new items
+                    mutation.addedNodes.forEach((item: HTMLElement) => observerPhotos.observe(item))
+                }
+            }
+        })
+        mutationPhotos.observe(photosListEl, {
+            childList: true,
+        })
+
+        // Observe existing elements
+        const existingPhotos = photosListEl.querySelectorAll('.house')
+        existingPhotos.forEach(el => observerPhotos.observe(el))
+
+
+        // Destroy
+        return () => {
+            observerPhotos && observerPhotos.disconnect()
+            mutationPhotos && mutationPhotos.disconnect()
+        }
     })
 </script>
 
@@ -220,7 +262,7 @@
     </section>
 
     {#if photos.length}
-        <section class="location-page__houses grid">
+        <section class="location-page__houses grid" bind:this={photosListEl}>
             {#each photos as { title, image: { id, title: alt }, slug, city, date_taken }, index}
                 <div class="house grid">
                     <div class="house__info">

src/routes/photos.svelte

@@ -244,16 +244,16 @@
                 isIntersecting && observerPhotos.unobserve(target)
             })
         }, {
-            threshold: 0,
+            threshold: 0.3,
             rootMargin: '0px 0px 0px'
         })
 
         // Photos MutationObserver
         mutationPhotos = new MutationObserver((mutationsList, observer) => {
-            // Use traditional 'for loops' for IE 11
             for (const mutation of mutationsList) {
+                // When adding new childs
                 if (mutation.type === 'childList') {
-                    console.log('A child node has been added or removed.')
+                    // Observe new items
                     mutation.addedNodes.forEach((item: HTMLElement) => observerPhotos.observe(item))
                 }
             }

src/style/organisms/_house.scss

@@ -13,9 +13,11 @@
 
     // Information
     &__info {
+        --delay: 0.2s;
         grid-column: 1 / span var(--columns);
         margin-bottom: 32px;
         padding: 0 20px;
+        overflow: hidden;
 
         @include bp (mob-lg) {
             max-width: min(540px, 85vw);
@@ -27,11 +29,20 @@
             max-width: 800px;
         }
 
+        h2 {
+            opacity: 0;
+            transform: translate3d(0, 25%, 0);
+            transition: transform 1.2s var(--ease-quart), opacity 1.2s var(--ease-quart);
+            transition-delay: var(--delay);
+        }
         .info {
             display: block;
             margin-top: 16px;
             color: $color-lightgray;
             line-height: 1.5;
+            opacity: 0;
+            transition: opacity 1.2s var(--ease-quart);
+            transition-delay: var(--delay);
 
             @include bp (sm) {
                 margin-top: 24px;
@@ -57,6 +68,8 @@
         position: relative;
         display: block;
         grid-column: 1 / span 17;
+        opacity: 0;
+        transition: opacity 2s var(--ease-quart);
 
         @include bp (sm) {
             border-radius: 8px;
@@ -69,8 +82,40 @@
         img {
             display: block;
             width: 100%;
-            height: auto;
-            object-fit: contain;
+            height: 100%;
+            object-fit: cover;
+            transform: scale3d(1.125, 1.125, 1.125);
+            transition: transform 2s var(--ease-quart), opacity 1.2s var(--ease-quart);
+            will-change: transform;
+        }
+
+        // Scale down image on hover
+        a:hover {
+            img {
+                opacity: 0.6;
+                transform: scale3d(1.03, 1.03, 1.03) !important;
+                transition-duration: 1.2s;
+            }
+        }
+    }
+
+    // Visible state
+    &.is-visible {
+        .house__info {
+            h2 {
+                opacity: 1;
+                transform: translate3d(0,0,0);
+            }
+            .info {
+                opacity: 1;
+            }
+        }
+        .house__photo {
+            opacity: 1;
+
+            img {
+                transform: scale3d(1,1,1);
+            }
         }
     }