Javascript based lexer

The problem is, we don't see syntax errors. For me I can write HTML files with javascript source an run them. But you don't see often errors... maybe you get a blank screen but no message. The result is we need to search every file for a syntax fault. 

Maybe it would be a very nice feature to add a javascript based lexer ( like Jison ). People could write custom lexers ( or you provide some for base langauges like js ), that could check the current selected file. Maybe a button in the upper right corner, check syntax or something like else. The file content would be send through a small javascript ( the instantiated jison parser ) and this could give us error informations and syntax faults with line number and enhanced descriptions.

Feel free to discuss about that idea :D

Greets Alex