update readme

readme.md

@@ -1,25 +1,17 @@
 # DataExtracter Help
 ----------------------------
 
-DataExtracter helps you quickly extract data from any web pages. All you need to do is:
+DataExtracter helps you quickly extract data from any web pages. 
+
+All you need to do is:
 
 - Find out the selectors (JQuery selectors) for target data
-- Call Extractor methods in `extension backgroud page console`, as introduced bellow.
-
-Where is the extension backgroud page console?
-
-Goto <chrome://extensions/> and click `backgroud page` link of the extension
-
- ![](images/extnsion.png)
-
-In the opening window, find `Console`, and type your scripts.
+- Type scripts in the console of `extension backgroud page`, as introduced bellow.
 
  ![](images/console.png)
 
 ## Qucik Start
 
-
-
 Extract current page
 ```js
 new Extractor().task(".list-item", ["a.title", "p.content"]).start();
@@ -43,7 +35,7 @@ Extract specified pages (1,3,5)
 new Extractor().task(".list-item", ["a.title", "p.content"], "http://sample.com/?pn=${page}", [1, 3, 5]).start();
 ```
 
-## Extractor.task() Signitures:
+## Extractor.task() Signitures
 
 ```ts
 // a task extracting data from current page
@@ -58,13 +50,17 @@ task(itemsSelector:string, fieldSelectors:string[], urls:string[])
 task(itemsSelector:string, fieldSelectors:string[], urls:ExractResult)
 ```
 
-## Advanced Usage:
+## Advanced Usage
 
-### Stop tasks
+### Stop Tasks
 
-The only way to stop tasks before its finish, is `Closing the Tab` which runs tasks.
+Tasks wait for their target elements' appearance, given some elements were loaded asynchronously.
 
-### Extract attributes. 
+But if you typed wrong selectors, the task waits forever for  elements which don't exists.
+
+The only way to stop tasks before its finish, is `Closing the host tab`.
+
+### Extract Attributes.
 
 e.g.: link text and target (use 'selector@attribute')
 
@@ -72,9 +68,9 @@ e.g.: link text and target (use 'selector@attribute')
 new Extractor().task('.list-item', ['a.title', 'a.title@href']).start();
 ```
 
-### Use task chain. 
+### Use Task Chain.
 
-e.g.: Collect links from `http://sample.com/abc` & Extract data of each link
+e.g.: Collect links from `http://sample.com/abc`, then, Extract data of each link
 
 ```js
 new Extractor()
@@ -83,7 +79,7 @@ new Extractor()
     .start();
 ```
 
-### Save result of any task
+### Save Result of Any Task
 
 To a multiple task (chain) Extractor `e`:
 
@@ -96,21 +92,21 @@ e.task('.search-list-item', ['.item a@href'], ["http://sample.com/abc"])
 
 User will be asked to save  the final result when it finishes.
 
-You may want to save another task's result, other than the final:
-
-```js
-// save the result of first task
-// that is, a list of urls
-e.save(1)
-```
-
 Incase you want to save it again, use:
 
 ```js
 e.save()
 ```
 
-### Restart tasks
+You may want to save another task's result, other than the final:
+
+```js
+// save the result of first task
+// to the example above, that is a list of urls
+e.save(1)
+```
+
+### Restart Tasks
 
 In cases some later task fails, you don't need to restart all task.