diff --git a/manifest.json b/manifest.json
index 9f07b43..1062617 100755
--- a/manifest.json
+++ b/manifest.json
@@ -1,7 +1,7 @@
 {
   "manifest_version": 2,
   "name": "Data Extracter",
-  "version": "0.0.1",
+  "version": "0.1.0",
   "author": "jebbs",
   "description": "Extract data from web page elements as sheet.",
   "icons": {
@@ -19,7 +19,8 @@
       "scripts/background.js",
       "scripts/result.js",
       "scripts/tools.js",
-      "scripts/extract.js"
+      "scripts/extract.js",
+      "scripts/extractor.js"
     ],
     "persistent": false
   },
diff --git a/scripts/extractor.js b/scripts/extractor.js
new file mode 100644
index 0000000..1be0b7b
--- /dev/null
+++ b/scripts/extractor.js
@@ -0,0 +1,111 @@
+class Exractor {
+    constructor() {
+        this._tasks = [];
+        this._results = {};
+    }
+    /**
+     * Add a task to Extractor. \n
+     * One Extractor could has multiple tasks, which orgnized in a task chian.
+     * Later task will use previous task result as input (target url list).
+     * So only the first task can have target url arguments, while later tasks can't.
+     * @param {...any} args itemsSelector, fieldSelectors, and more args to specify target urls.
+     */
+    task(...args) {
+        if (!testArgs(...args))
+            throw new Error(`Invalid call arguments.\n\n${signitures}\n\n`);
+        // given >2 arguments means the task specifies target page, 
+        // so it won't accept last task result as url list.
+        // in this case, former tasks are useless, can be cleared.
+        if (args.length > 2) this.clear();
+        this._tasks.push(args);
+        return this;
+    }
+    /**
+     * Clear tasks and caches.
+     */
+    clear() {
+        this._tasks = [];
+        this._results = [];
+    }
+    /**
+     * Start the task chain.
+     */
+    async start() {
+        if (!this._tasks.length) {
+            console.log('No task to run.');
+            return;
+        }
+        return this._tasks.reduce((pms, args, i, tasks) => {
+            return pms.then(
+                result => {
+                    if (result === undefined) return getData(...args);
+                    this._results[tasks[i - 1]] = result;
+                    return getData(...args, result);
+                });
+        }, Promise.resolve(undefined)).then(
+            result => {
+                this._results[this._tasks[this._tasks.length - 1]] = result;
+                this.save();
+            }
+        );
+    }
+    /**
+     * restart from specified task, but don't restart the previous tasks.
+     * @param {number} taskid from which restart the tasks
+     */
+    async restart(taskid) {
+        taskid = this._checkTaskId(taskid, 1);
+        if (!taskid) return;
+        if (taskid == 1) {
+            this.start();
+            return;
+        }
+        let cache = this._results[this._tasks[taskid - 2]];
+        if (!cache) {
+            console.log(`No result cache for task (id ${taskid}). \nMake sure call ".start()" before ".restart()"?`);
+            return;
+        }
+        return this._tasks.slice(taskid - 1).reduce((pms, args, i, tasks) => {
+            return pms.then(
+                result => {
+                    this._results[tasks[i - 1]] = result;
+                    return getData(...args, result);
+                });
+        }, Promise.resolve(cache)).then(
+            result => {
+                this._results[this._tasks[this._tasks.length - 1]] = result;
+                this.save();
+            }
+        );
+    }
+    /**
+     * Save result of a task
+     * @param {number} taskid which task id to save.
+     */
+    save(taskid) {
+        taskid = this._checkTaskId(taskid, this._tasks.length);
+        if (!taskid) return;
+        const result = this._results[this._tasks[taskid - 1]];
+        if (!result) {
+            console.log(`No task result for id (${taskid}). Forget to call ".start()"?`);
+            return;
+        }
+        if (confirm(
+                `Click confirm to download if the sample data looks good (${result.data.length} items)：\n\n${result.toString(50) || "- Empty -"}`
+            )) {
+            saveFile(result, "text/csv");
+        }
+    }
+    _checkTaskId(id, defaultId) {
+        if (!this._tasks.length) {
+            console.log("No task found.");
+            return 0;
+        }
+        if (defaultId && id === undefined || this.task === null) id = defaultId;
+        if (isNaN(id) || id < 1 || id > this._tasks.length) {
+            console.log(`Invalid task id. Rang(1-${this._tasks.length})`);
+            return 0;
+        }
+        return id
+    }
+}
\ No newline at end of file