availablity check before run on active tab

scripts/background/actions.js

@@ -110,16 +110,17 @@ function extractTabData(tab, itemsSelector, fieldSelectors) {
 }
 
 /**
- * get report in from the target tab, usually used to detect if the content script is ready.
+ * ping target tab, usually used to detect if the content script is ready.
  * @param {any} tab target tab
- * @returns {Promise<string>} a promise of the report in message
+ * @returns {Promise<boolean>} a promise of boolean value indicates if ping success
  */
-function reportIn(tab) {
+async function ping(tab, count = 1) {
     let req = {
         action: ACTION_REPORT_IN
     }
     let cond = r => r == req.action;
-    return sendMessage(tab, req, 'Check tab availability...', cond);
+    let pong = await sendMessage(tab, req, 'Check tab availability...', cond, 1000, count).catch(() => { });
+    return pong == ACTION_REPORT_IN;
 }
 
 /**

scripts/background/extractor.js

@@ -56,6 +56,11 @@ class Extractor {
             tab = await createTab(task.urls[0], false);
         } else {
             tab = await getActiveTab(true) || await getActiveTab(false);
+            let succ = await ping(tab);
+            if (!succ) {
+                console.log('Cannot contact with active tab.');
+                return;
+            }
         }
         this._running = true;
         return this._tasks.reduce((pms, task, i) => {

scripts/background/messaging.js

@@ -4,12 +4,15 @@
  * @param {object} tab the table where to send the message
  * @param {object} req the request data.
  * @param {function} cond success condition function, r:any=>boolean
- * @param {number} interval interval for detecting
+ * @param {number} interval retry interval, default: 500ms.
+ * @param {number} limit retry limit, default: 0, no limit.
  * @param {string} log messages logged to console.
  * @return {Promise} a promise of the response.
  */
-function sendMessage(tab, req, log, cond, interval) {
+function sendMessage(tab, req, log, cond, interval, limit = 0) {
     interval = interval || 500;
+    limit = limit && !isNaN(limit) ? limit : 0;
+    count = 0;
     return new Promise((resolve, reject) => {
 
         loop();
@@ -22,6 +25,11 @@ function sendMessage(tab, req, log, cond, interval) {
                 return;
             }
 
+            if (limit && count >= limit) {
+                reject(`sendMessage loop limit ${limit} reached.`);
+                return;
+            }
+            count++;
             chrome.tabs.sendMessage(tab.id, req, r => {
                 // check error but do nothing.
                 // do not interrupt promise chains even if error, or the task always fail when: