JavaScript is very important for the world wide web universe. But JavaScript support on Vim is not update very often. So I keep contribute to the Vim community. One of my contribution is yajs.vim(Yet Another JavaScript Syntax). One of the most powerful JavaScript syntax highlight plug-in for Vim now. It supports almost every new syntax from ECMAScript 2015, JSDoc, lots of new Web API and fixed several old issues. This talk will first explain Vim syntax system. The design, concept and limitation of it. Then will share the problems encountered during the development in this environment. And finally, how I solved these problems.