JavaScript is most widely used language for Web programming, general purpose computing and cross platform applications. As the computational power becomes higher and the web technologies are getting more complex, the performance of the JavaScript engine is needed to improve much higher than yesterday. Also mobile devices will be a main device among the variousWeb connecting devices, we figure out the performance gap of JavaScript engine between the mobile and desktop environment to understand the gap. In addition to dealing with this performance gap, we study the architectural characteristics influenced by the JavaScript language in a mobile architecture. As a result, we propose branch prediction scheme and branch target buffer scheme that handle the behavior of JavaScript compile and execution.