How can I make a yup number accept nullable values?

Question

I have the following yup check:

nrOfApples: yup.number().min(0).max(999),

And right now if I leave the field blank, it validates as false. Is there any way to make yup.number() accept empty values? I have tried:

yup.number().nullable()

But it doesn't seem to work. Any ideas on how I can make such thing happen?

Aquamarine

Answer 1

You have to pass true to nullable -

nrOfApples: yup.number().min(0).max(999).nullable(true);

From: https://github.com/jquense/yup/issues/500

Working example: https://runkit.com/xdumaine/5f2816c75a0ba5001aa312b2

Note that if you add required().nullable(true) the required overrides the nullable and null will not validate.

Update:

You can use a transform to convert the NaN value into null. I updated the runkit with this:

const contactSchema = yup.object({
  name: yup.string()
    .required(),
  nrOfApples: yup
    .number()
    .min(0)
    .max(999)
    .nullable(true)
    // checking self-equality works for NaN, transforming it to null
    .transform((_, val) => val === Number(val) ? val : null) 
})

Izard

Hi @xdumaine, thanks for your response. However, when the field is left as empty, the value that it returns is NaN instead of null, so .nullable(true) is not working in this case. – Aquamarine

The suggested solution did not work for me but thankfully the runkit link provided contained a change. I will suggest an edit but just in case swap the transform function call to the following .transform((_, val) => val ? Number(val) : null) – Leaguer

@Izard Thanks for amazing answer, very comman to come this situation but very challaging with Yup library to validate number fields. – Creeps

This works up until someone enters some nonsense like -+1e into the number input, which will behind the scenes converts to null (imo not good ux). Can't tell the difference between nonsense and a null input in the transform bc they both are passed in as NaN – Sotted

Answer 2

also this worked for me,

validation: yup.string().nullable()

Marj