How to chain express-validator based on query values?

Question

I am trying to find a solution to chain conditions based on the query values passed to the route.

Task1:
// if value for query A = noIdNeeeded, then i do not need to search for a second queryB
/endpoint?queryA=noIdNeeded

Task2:
// if value for query A = idNeeded, then i need to ensure second queryB exists
/endpoint?queryA=idNeeded&queryB=SomeId

I am having trouble with the writing parameter for Task 2.

For task 1 i have use this logic and works fine [query('page').exists().notEmpty().isIn(seoPageTypes),]

So far I have seen there is an if clause that we can use probably (link) however implementing this has been a challenge due to lack of examples and no prior experience.

If anyone can guide on how to do this correctly or any hint is much appreciated.

Answer 1

Make sure you have a new version of express-validator installed.

The following should do your job.

query('queryA').exists().notEmpty().isIn(seoPageTypes),
query('queryB')
    .if(query('queryA').equals('idNeeded'))
    .exists().notEmpty().withMessage('queryB must exist'),

Another approach is to use a custom validator

query('queryA').exists().notEmpty().isIn(seoPageTypes)
    .custom((value, {req}) => {
        if (value === "idNeeded" && !req.query.queryB) {
            throw new Error('queryB must exist');
        }
        return true;
    }),

Use what suits you more :)