Tina allows client-side validation using a validation function. This function returns a string error message if the value is invalid or null if the field is valid.

To include other field values of the form in the validation, a data argument can be used.

Example

Validate the length of a `string` field

{
  label: "Title",
  name: "title",
  type: "string",
  ui: {
    validate: (value, data)=>{
      const lengthOfTitle = value?.length || 0
      const lengthOfDescription = data?.description?.length || 0
      if(lengthOfTitle >= lengthOfDescription){
        return 'The description must be longer than the title'
      }
    }
  }
}

The following schema types support the use of validate:

• string
• datetime
• boolean
• image
• number