Greetings!
Sure, can create join/cancel button and controller in your Ionic project according to your requirements.
Relevant Skills and Experience
Have thorough understanding of HTML5, CSS3, Sass, Angular JS, MySQL, JSON and Cordova.
Proposed Milestones
$100 CAD - Tentative Estimate
$100 CAD - Tentative Estimate
Can you please more details and link of your existing webapp ?