Discussion on: React form validation with Hook in 5kB

Not bad. But not a fan of:

ref={register({
validate: {
positiveNumber: value => parseFloat(value) > 0,
lessThanHundred: value => parseFloat(value) < 200
}
})}

because it seems wordier than

ref={register({
positiveNumber: value => parseFloat(value) > 0,
lessThanHundred: value => parseFloat(value) < 200
})}

though I understand you are using keyword required in a different way, like

ref={register({
required: true,
maxLength: 80,
validate: {
positiveNumber: value => parseFloat(value) > 0,
lessThanHundred: value => parseFloat(value) < 200
}
})}

even though I think it would be OK to crush them together

ref={register({
required: true,
maxLength: 80,
positiveNumber: value => parseFloat(value) > 0,
lessThanHundred: value => parseFloat(value) < 200
})}

just to save client code keystrokes.

Also it's unclear to me how it maps values from form to model and back, espeically if the mapping isn't simple. Like, a checkbox that maps to a Date field, setting it to 60 days from now, or null, depending if the checkbox is checked.