express-validator to validate parameter which is an array

Question

I am using express-validator to validate POST data in my express application. I have a form which has a select where in user can select multiple options:

<select name="category" multiple id="category">
    <option value="1">category 1 </option>
    .......
</select>

The payload after submitting form shows me this if I select multiple values:

...&category=1&category=2&....

Now, in my Express application I try to validate it like this:

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

But, even after I send multiple values I always get the error - category cannot be empty. If I print my variable as req.body.category[0] - I get the data. But, somehow not able to understand the way I need to pass this to my validator.

Answer 1

You may need to create your own custom validator;

expressValidator = require('express-validator');
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();