v1.8.0
New nullable rule attribute in #185
const schema = {
age: { type: "number", nullable: true }
}
v.validate({ age: 42 }, schema); // Valid
v.validate({ age: null }, schema); // Valid
v.validate({ age: undefined }, schema); // Fail because undefined is disallowed
v.validate({}, schema); // Fail because undefined is disallowed