Add localstorage management

mobile/www/js/index.js

@@ -0,0 +1,50 @@
+const baseUrl = "http://localhost:3000/";
+
+let feData = JSON.parse(localStorage.getItem("feData"));
+
+function updateData(data) {
+    if (Object.keys(data).length > 0) {
+        localStorage.setItem("feData", JSON.stringify(data));
+        feData = data;
+    }
+}
+
+if (feData != null) {
+    fetch(baseUrl + "update", {
+        method: "POST",
+        body: JSON.stringify({version: feData.version}) ,
+        headers: {
+            'Content-Type': 'application/json'
+        },
+    })
+        .then(res => {
+            if (res.ok) {
+                return res.json();
+            } else {
+                console.log(res);
+            }
+        })
+        .then(data => {
+            updateData(data);
+        })
+        .catch(err => {
+            console.log(err);
+        });
+} else {
+    fetch(baseUrl + "all")
+        .then(res => {
+            if (res.ok) {
+                return res.json();
+            } else {
+                console.log(res);
+            }
+        })
+        .then(data => {
+            updateData(data);
+        })
+        .catch(err => {
+            console.log(err);
+        });
+}
+
+