requestValidator.js

var _ = require("underscore");

var parse = {
  string:function(val) {
    return val.toString();
  },
  int:function(val) {
    var num = parseInt(val);
    if(isNaN(num))
      return 0;
    else
      return num
  },
  float:function(val) { 
    var num = parseFloat(val);
    if(isNaN(num))
      return 0;
    else
      return num
  }
};

exports.makeValidator = function(reqMap) {
  return function(req,res,next) {
    var proceed = false
    , reqKeys = _.keys(req.body);

    if(reqMap.canOnly) {
      if(reqMap.canOnly.length === reqKeys.length) {

        proceed = _.chain(reqKeys)
              .intersection(reqMap.canOnly)
              .value().length === reqMap.canOnly.length;
      }
    } else if(reqMap.must) {

      proceed = _.chain(reqMap.must)
            .map(function(key) {
              return _.contains(reqKeys,key);
            })
            .every()
            .value();
    } else {
      proceed = true;
    }   
    
  

    if(proceed) {
      if(reqMap.omit) {
        req.body = _.omit(req.body,reqMap.omit);
      }
      if(reqMap.types) {
        _.each(reqMap.types,function(type,key) {
          if(_.has(req.body,key)) {
            req.body[key] = parse[type](req.body[key]);
          }
        });
      }
      next();
    } else {
      res.send(400);
    }
  }
};