attr('checked', 'checked') did not work for me

I use jQuery version 2+
I quote from jQuery website: The difference between attributes and properties can be important in specific situations. Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
Merge pull request #5 from StudioWolfox/patch-1

attr('checked', 'checked') did not work for me