Initial commit

frontend/src/lib/functions/observer.ts

@@ -0,0 +1,27 @@
+export default function inView(node, params = { threshold: 0 }) {
+    let observer
+
+    const handleIntersect = (e) => {
+        const v = e[0].isIntersecting ? "enter" : "exit"
+        node.dispatchEvent(new CustomEvent(v))
+    }
+
+    const setObserver = ({ threshold }) => {
+        const options = { threshold }
+        if (observer) observer.disconnect()
+        observer = new IntersectionObserver(handleIntersect, options)
+        observer.observe(node)
+    }
+
+    setObserver(params)
+
+    return {
+        update(params) {
+            setObserver(params)
+        },
+
+        destroy() {
+            if (observer) observer.disconnect()
+        },
+    }
+}