Here are three plugins which can do the job really well for my site.
1. WP Deferred JavaScripts
2. Asynchronous Javascript
3. WP Fastest Cache
Before I installed both the plugins, this was the results from Google PageSpeed Insights:
After installed the first plugin, WP Deferred Javascripts at: https://wordpress.org/plugins/wp-deferred-javascripts/
This is the results from PageSpeed Insights:
This is the results from Web Page Test:
Then I installed the second one called Asynchronous Javascript at: http://wordpress.org/plugins/asynchronous-javascript/
This the results from Google PageSpeed Insights:
The results still remains the same, but it has reduced the number of blocking JavaScript.
The third plugin is WP Fastest Cache. It is at: http://wordpress.org/plugins/wp-fastest-cache/
This is the results after installing this plugin:
* Here is how to increase page speed by leverage browser caching guide.