Question About relative path

[Lautitia]

If i have the directory as following

--libs
    |- a.js
--run
    |-run.js

code in run.js

        var needless = require('needless');
        var libpath = '../libs/a';
        needless(libpath);
        require(path).callFunction(xxx)

then run run/run.js

        node run/run.js

node will report:

        Cannot find module '../libs/a'

I check the code, it seems the relative path '../libs/a' hasn't been process proper,but if i move run.js to upper level directory and modify the '../libs/a' to './libs/a' then it's ok.