1 files changed, 51 insertions, 0 deletions
diff --git a/src/static/lazy-loading.js b/src/static/lazy-loading.js
new file mode 100644
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+++ b/src/static/lazy-loading.js
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+// Lazy loading! Roll your own. Woot.
+// This file includes a 8unch of fall8acks and stuff like that, and is written
+// with fairly Olden JavaScript(TM), so as to work on pretty much any 8rowser
+// with JS ena8led. (If it's disa8led, there are gener8ted <noscript> tags to
+// work there.)
+
+var observer;
+
+function loadImage(image) {
+    image.src = image.dataset.original;
+}
+
+function lazyLoad(elements) {
+    for (var i = 0; i < elements.length; i++) {
+        var item = elements[i];
+        if (item.intersectionRatio > 0) {
+            observer.unobserve(item.target);
+            loadImage(item.target);
+        }
+    }
+}
+
+function lazyLoadMain() {
+    // This is a live HTMLCollection! We can't iter8te over it normally 'cuz
+    // we'd 8e mutating its value just 8y interacting with the DOM elements it
+    // contains. A while loop works just fine, even though you'd think reading
+    // over this code that this would 8e an infinitely hanging loop. It isn't!
+    var elements = document.getElementsByClassName('js-hide');
+    while (elements.length) {
+        elements[0].classList.remove('js-hide');
+    }
+
+    var lazyElements = document.getElementsByClassName('lazy');
+    if (window.IntersectionObserver) {
+        observer = new IntersectionObserver(lazyLoad, {
+            rootMargin: '200px',
+            threshold: 1.0
+        });
+        for (var i = 0; i < lazyElements.length; i++) {
+            observer.observe(lazyElements[i]);
+        }
+    } else {
+        for (var i = 0; i < lazyElements.length; i++) {
+            var element = lazyElements[i];
+            var original = element.getAttribute('data-original');
+            element.setAttribute('src', original);
+        }
+    }
+}
+
+document.addEventListener('DOMContentLoaded', lazyLoadMain);