Just Do it

太让人震惊了，JS可以加载本地库文件。
在Firefox下面

Components.utils.import("resource://gre/modules/ctypes.jsm");
 
var lib = ctypes.open("C:\\WINDOWS\\system32\\user32.dll");
 
/* Declare the signature of the function we are going to call */
var msgBox = lib.declare("MessageBoxW",
                         ctypes.winapi_abi,
                         ctypes.int32_t,
                         ctypes.int32_t,
                         ctypes.jschar.ptr,
                         ctypes.jschar.ptr,
                         ctypes.int32_t);
var MB_OK = 0;
 
var ret = msgBox(0, "Hello world", "title", MB_OK);
 
lib.close();

详细见：JS－ctypes