Here is my explanation based on Jonathan solutions. I tried his solution and succeeded but took more time. So I thought to explain steps I followed so that it can save someone's time.
Steps:-
1) First install cordova if not already installed using Cordova cli as below
Note: you must install node.js if not already installed.
npm install -g cordova
or
sudo npm install -g cordova
2) Go to the directory where you maintain your source code, and run a command such as the following:
$ cordova create hello com.example.hello HelloWorld
The first argument specifies a hello directory to be generated for your project. Its www subdirectory houses your application's home page, along with various resources under css, js, and img, which follow common web development file-naming conventions. The config.xml file contains important metadata needed to generate and distribute the application.
The other two arguments are optional: the com.example.hello argument provides your project with a reverse domain-style identifier, and the HelloWorld provides the application's display text
cd hello
cordova platform add ios
cordova plugin add https://github.com/jonathannaguin/BarcodeScanner.git
cordova build
cordova prepare
3) remove all files from www folder except following
confix.xml
cordova_plugins.js
cordova.js
plugins (folder contaning barcodescanner.js)
and your own index.html,js,css files
I will be glad if it helps someone.