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validation_and_transforms.md

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✨ Validation / Transforms

Validation

The great thing about binary encoders is that data is implicitly type-validated, however, you can also add custom validation rules using setValidation():

const UserMessage = defineFormat({
  uuid: Type.String,
  name: Optional(Type.String),
  // …
})
.setValidation({
  uuid: (x) => {
    if (!isValidUUIDv4(x)) {
      throw new Error('Invalid UUIDv4: ' + x)
    }
  }
})

Transforms

You can also apply additional encode/decode transforms.

Here is an example where we're stripping out all whitespace:

const PositionMessage = defineFormat({ name: Type.String })
  .setTransforms({ name: a => a.replace(/\s+/g, '') })

let binary = PositionMessage.encode({ name: 'Hello  There' })
let data = PositionMessage.decode(binary)

data.name
  // "HelloThere"

Unlike validation, transforms are applied asymmetrically.

The transform function is only applied on encode(), but you can provide two transform functions.

Here is an example which cuts the number of bytes required from 10 to 5:

const PercentMessage = defineFormat(null, { value: Type.String })
  .setTransforms({
    value: [
      (before) => before.replace(/\$|USD/g, '').trim(),
      (after) => '$' + after + ' USD'
    ]
  })

let binary = PercentMessage.encode({ value: ' $45.53 USD' })
let data = PercentMessage.decode(binary)

binary.byteLength
  // 5

data.value
  // "$45.53 USD"