# DataExtracter Help
----------------------------

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.

 ![](images/console.png)

## Qucik Start



Extract current page
```js
new Extractor().task(".list-item", ["a.title", "p.content"]).start();
```

Extract multiple pages (1-10, interval 1)

```js
new Extractor().task(".list-item", ["a.title", "p.content"],"http://sample.com/?pn=${page}", 1, 10, 1).start();
```

Extract multiple urls (list)

```js
new Extractor().task(".list-item", ["a.title", "p.content"],["http://sample.com/abc","http://sample.com/xyz"]).start();
```

Extract specified pages (1,3,5)

```js
new Extractor().task(".list-item", ["a.title", "p.content"], "http://sample.com/?pn=${page}", [1, 3, 5]).start();
```

## Extractor.task() Signitures:

```ts
// a task extracting data from current page
task(itemsSelector:string, fieldSelectors:string[])
// a task extracting data from a range of pages
task(itemsSelector:string, fieldSelectors:string[], urlTemplate:string, from:number, to:number, interval:number)
// a task extracting data from a list of pages
task(itemsSelector:string, fieldSelectors:string, urlTemplate:string, pages:number[])
// a task extracting data from a list of pages
task(itemsSelector:string, fieldSelectors:string[], urls:string[])
// a task extracting data of urls which extracted from last task result
task(itemsSelector:string, fieldSelectors:string[], urls:ExractResult)
```

## Advanced Usage:

### Stop tasks

The only way to stop tasks before its finish, is `Closing the Tab` which runs tasks.

### Extract attributes. 

e.g.: link text and target (use 'selector@attribute')

```js
new Extractor().task('.list-item', ['a.title', 'a.title@href']).start();
```

### Use task chain. 

e.g.: Collect links from `http://sample.com/abc` & Extract data of each link

```js
new Extractor()
    .task('.search-list-item', ['.item a@href'], ["http://sample.com/abc"])
    .task('list-item', ["a.title", "p.content"])
    .start();
```

### Save result of any task

To a multiple task (chain) Extractor `e`:

```js
e = new Extractor()
e.task('.search-list-item', ['.item a@href'], ["http://sample.com/abc"])
    .task('list-item', ["a.title", "p.content"])
    .start();
```

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

In cases some later task fails, you don't need to restart all task.

Here we have 2 tasks:

```js
e = new Extractor()
e.task('.search-list-item', ['.item a@href'], ["http://sample.com/abc"])
    .task('list-item', ["a.title", "p.content"])
    .start();
```

Suppose the second task fails, we can restart and continue from the task 2:

```js
e.restart(2);
```

If you'd like restart all task, use:

```js
e.start();
// or
e.restart();
```