const jkt = require('jkt')
const Person = jkt`
name: String
age: Number
birthday: ${jkt.trans.custom(val => "I'm old man =,=")}
`
const nina = Person({
name: "Nina",
age: "25",
birthday: new Date() // this will produce "I'm old man =,="
});
console.log(nina.birthday) // "I'm old man =,="
console.log(nina.j().birthday) // "I'm old man =,="