Custom express validators via express-validator

validate.js

// http://stackoverflow.com/questions/37339479/express-validator-to-validate-paramenter-which-is-an-array#answer-37342458
var expressValidator = require('express-validator');
var validator = require('validator');

app.use(expressValidator({
  customValidators: {
     isArray: function(value) {
        return Array.isArray(value);
     },
     notEmpty: function(array) {
        return array.length > 0;
     }
     gte: function(param, num) {
        return param >= num;
     }
  }
}));

req.checkBody('category', 'category cannot be empty').isArray().notEmpty();