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

Try this:

router.post('/your-url', 
      [
        check('category').custom((options, { req, location, path }) => {
            if (typeof category === 'object' && category && Array.isArray(category) && category.length) {
              return true;
            } else {
              return false;
            }
          })
    ],
    controller.fn);