HTML template integration

Hi every one, im new to wordpress…
i have a doubt that is there any possibilities to integrate a template which is developed in HTML ,JavaScript…

actually my client wants look and feel like he have a template in html javascript… please let me know whether it is possible to integrate the template or else downloading a free theme and doing modifications is the only way?…
a good and quick replay will appreciated…
please assist me asap…
thank you…