function requireModel(filePath, cb) {
            //check if file exist. if not return error
            fs.exists(filePath, function (exists) {
                if (!exists) {
                    return cb(new Error("Requested Model Not Found!"));
                }

                libProduct.model = require(filePath);
                return cb(null, libProduct);
            });
        }
function requireModel(filePath, cb) {
            
            fs.exists(filePath, function (exists) {
                if (!exists) {
                    return cb(new Error("Requested Model Not Found!"));
                }

                libProduct.model = require(filePath);
                return cb(null, libProduct);
            });
        }
function requireModel ( filePath , cb ) { //check if file exist. if not return error fs . exists ( filePath , function ( exists ) { if ( ! exists ) { return cb ( new Error ( "Requested Model Not Found!" ) ) ; } libProduct . model = require ( filePath ) ; return cb ( null , libProduct ) ; } ) ; }
checks if model file exists, requires it and returns it.
@param filePath
@param cb
checks if model file exists requires it and returns it .