default

Sets the value if it is empty: missing, null or an empty string. Other values, including 0, are kept.

Live example · edit rules or inputOpen in playground

rules

{
    age: { default: 18 },
    country: { default: 'UA' }
}

{ age: { default: 18 }, country: { default: 'UA' } }

input

{
    country: 'PL'
}

{ country: 'PL' }

Validoutput

{
  "age": 18,
  "country": "PL"
}