Added proper alert messages and improved security of import file.

scripts/background.js

@@ -0,0 +1,76 @@
+const regexp = /^[a-zA-Z0-9-_]+$/; // Alphanumeric, dash, underscore
+
+
+const alertMessage = (type, message) => {
+    let msgTag    = document.getElementById("allertMessage");
+    let text      = document.createTextNode(message);
+    let fontColor = "rgba(255, 255, 255, 1)";
+    let bgColor   = "";
+
+    if (type === "success") {
+        bgColor   = "rgba(72, 125, 25, 1)";
+    } else if (type === "warning") {
+        bgColor   = "rgba(195, 123, 0, 1)";
+    } else if (type === "error") {
+        bgColor   = "rgba(125, 45, 25, 1)";
+    }
+
+    msgTag.style.backgroundColor = bgColor;
+    msgTag.style.color           = fontColor;
+    msgTag.style.display         = "block";
+    msgTag.append(text);
+
+    setTimeout(function () {
+        let msgTag           = document.getElementById("allertMessage");
+        msgTag.innerHTML     = "";
+        msgTag.style.display = "none";
+    }, 4000);
+}
+
+const processor = (obj, enteryName = '') => {
+    let data  = obj.target.result;
+
+    do {
+        enteryName = prompt("What is this session's name? Allowed: a-z, A-Z, -, _", '' + enteryName);
+        if (enteryName == null) break
+    } while (enteryName.search(regexp) == -1);
+
+    if (enteryName) {
+        try {
+            console.log("Importing session...");
+            JSON.parse(data);
+            browser.storage.local.set({[enteryName]: data});
+            alertMessage("success", "Imported file successfully.")
+        } catch (e) {
+            alertMessage("error", "Failed to import data. Not a JSON parsable file.");
+            return ;
+        }
+    } else {
+        alertMessage("warning", "Canceled import.");
+    }
+};
+
+document.getElementById("inputId").onchange = (e) => {
+    let size = e.target.files.length;
+    let fileArry = e.target.files;
+
+    for (var i = 0; i < size; i++) {
+        let reader = new FileReader();
+        let name   = fileArry[i].name;
+        name = name.split(".")[0];
+
+        reader.onloadend = (obj) => { processor(obj, name); };
+
+        if (fileArry[i].type == "application/json")
+            reader.readAsText(fileArry[i], {encoding: "string"});
+    }
+};
+
+
+document.addEventListener("click", (e) => {
+    if (e.button == 0) {  // Left click
+        if (e.target.className == "container") {
+            document.getElementById("inputId").click();
+        }
+    }
+});