Front end development project for an existing application

We currently have an existing application and a full time development team. We need someone to assist in executing some specific design development with our team. We will provide access to the application, designs, and APIs. Code needs to be done in the system to simplify implementation by our team. Full instruction will be provided, but provider should be versed in front-end development, ideally including understanding javascript. This could be an hour or project compensation basis.