As you mentioned ocrad.js I assume you search for something in js/nodejs. Many others already recommended tesseract and OpenCV.
We have built a library around tesseract for character recognition and OpenCV (and other libraries) for preprocessing, all for node.js/io.js: https://github.com/creatale/node-dv
We open-sourced the library that we use for exactly that purpose: https://github.com/creatale/node-fv