shape.md

Shape

This document will show you:

• How to define a shape.
• How the descriptor properties of a type work with shapes.

There are 3 kinds of shapes, object, array and their combination.

Object Shape

Let us look into an example of the shape definition step by step.

import {shape} from 'skema'

const User = shape({
  // 1
  id: Number,
  // 2
  profile: shape({
    // 3
    birth: 'date',
    // 4
    name: 'string?'
  })
})

1. The user id is a number, and Number is an alias of the built-in number type.

2. To define a deep shape, just make the object deeper.

3. 'date' is also an alias

4. 'string?' is equivalent to:

type({
  type: 'string',
  optional: true
})

For more information about optional type, see optional section below.

const user = User.from({
  id: '123',
  profile: {
    birth: '1999-01-01',
    name: 'Jack'
  }
})

Then

• user.id is the number 123
• user.profile.birth is an Date object which time is 1999-01-01
• user.profile.name is 'Jack'

optional

And how about the given data without id.

User.from({
  profile: {
    birth: '1999-01-01',
    name: 'Jack'
  }
})
// throw Error
// - code: NOT_OPTIONAL
// - message: key 'id' is not optional
// - path: ['id']
// - key: 'id'

It throws an error, what happens?

The built-in type Number is not optional. If a property of a shape is not optional, and the given value does not contain the property, it will fail.

To fix this, you should either make the data right or change the shape:

shape({
  // use string syntactic suger
  id: 'number?'
})

shape({
  // inherit a skema
  id: type({
    type: Number,
    optional: true
  })
})

More information about Type Inheritance, see this example.

default

when

configurable

enumerable

writable

Array Shape