WebDriverJS -Selenium Runner On Node with Promise Mechanism

Agenda Of the Blog: Introduction of  WebDriverJS (not WebDriver)-A Selenium Runner on Node

What is WebDriverJS: A selenium Runner on NODE,Highly extendible,compatible with all common JavaScript Testing Framework,hugely used for Angular JS application.

WebDriverJS & WebDriver are Same:NO.
The above two are related but not the same.

How both are related but not the same:
A. WebDriverJS is the JavaScript Language bindings for WebDriver,It runs on NODE,It uses an own chain API to execute and handle Asynchronous Calls in specific and in right order.

B.In Addition to NODE, WebDriverJS may also be used directly in the browser by JSonWire Protocol Communication as the Other Language binding of WebDriver(i.e Java,Python,Ruby etc. etc.).One of The Advantages for running WebDriverJS in the browser is that it can control the browser running the Script,as long as The URL for the server and Session ID for the browser are known.

C.Unlike other language bindings,which all provide blocking APIs,WebDriverJS is purely Asynchronous,In order to track handle exceptions WebDriverJS makes extensive use of "Promises."
While there are various promise implementations are there for JS,the WebDriverJS promise is based on the proposal from CommonJS,which defines a promise as any object with a "then" function property.

Asynchronous Computation:Its a concept of passing a callback function that is called when the result becomes available at some later time ,rather than a function returning a result value immediately.

Example:

Browser Offers a primarily single thread runtime environment,so if you request your browser to fetch some information which takes 3 seconds,then the browser will not be able to do anything else than to wait for HTTP call.

So, Asynchronous call came to the picture to overcome this kind of scenarios.

Concept of Promise:The promise object is used for deferred and Asynchronous computation.

A promise is in one of three different states:

1.Pending: Promise's initial state.

2.Fulfilled: Representing promise's state of successful operation.

3.Rejected: Represents promises's failed operation.

How WebDriverJS works with Asynchronous calls:

WebDriverJS uses a wrapper for Promise called ControlFlow Class: 

A.It maintains a list of scheduled actions

B.The exposed functions in WebDriverJS do not actually do their stuffs,they just push the required actions into ControlFlow Class.

Example:

With Simple WebDriver with Java we write :

driver.get("www.xyzabc.com");

driver.findElement(By.id("k1")).sendKeys("WebDriver");

Using Promise we need to write the same like:

driver.get("www.xyzabc.com").   then(function() {
     return driver.findElement(By.id("k1"));
   }).
   then(function(k1) {
     return k1.sendKeys("WebDriver");   }).

By this way WebDriverJS is related with WebDriver,uses Promise,JSON Wire Protocol and handles Asynchronous Calls very efficiently.

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