kast

kast is a lightweight JSON transformation library that offers a set of utilities to filter, reshape, and manipulate JSON objects and arrays.

Installation

Install with your preferred package manager:

pnpm add @kalisio/check

npm install @kalisio/check

yarn add @kalisio/check

Examples

transform

NOTE

transform is a small data transformation pipeline that:

1. Converts data structures
2. Filters data
3. Applies field mappings
4. Converts values (units, types, dates)
5. Modifies object structure (pick / omit / merge)

• Rename Fields (Simple Mapping)

const data = { first_name: 'John', age: 30 }

const options = {
  mapping: {
    first_name: 'name'
  }
}

// Result
{ name: 'John', age: 30 }

• Filter Data

const data = [
  { name: 'John', age: 17 },
  { name: 'Jane', age: 25 }
]

const options = {
  filter: { age: { $gte: 18 } }
}

// Result
[
  { name: 'Jane', age: 25 }
]

• Convert String to Number

const data = { age: '42' }

const options = {
  unitMapping: {
    age: { asNumber: true }
  }
}

// Result
{ age: 42 }

• Format Dates

const data = { date: '2024-01-01' }

const options = {
  unitMapping: {
    date: {
      asDate: true,
      to: 'DD/MM/YYYY'
    }
  }
}

// Result
{ date: '01/01/2024' }

• Map Values and rename field

const data = { status: 1 }

const options = {
  mapping: {
    status: {
      path: 'statusLabel',
      values: {
        1: 'active',
        0: 'inactive'
      }
    }
  }
}

// Result
{ statusLabel: 'active' }

• Remove or keep fields

const data = {
  name: 'John',
  age: 30,
  password: 'secret'
}

const options = {
  omit: ['password']
}

// Result
{ name: 'John', age: 30 }

const options = {
  pick: ['name']
}

// Result
{ name: 'John' }

• Merge additional data

const data = { name: 'John' }

const options = {
  merge: { country: 'FR' }
}

// Result
{ name: 'John', country: 'FR' }

• Convert array of arrays to objects

const data = [
  ['John', 30],
  ['Jane', 25]
]

const options = {
  toObjects: ['name', 'age']
}

// Result
[
  { name: 'John', age: 30 },
  { name: 'Jane', age: 25 }
]

• Full example

const data = [
  { first_name: 'John', age: '20', status: 1 },
  { first_name: 'Jane', age: '17', status: 0 }
]

const options = {
  filter: { age: { $gte: 18 } },
  mapping: {
    first_name: 'name',
    status: {
      path: 'statusLabel',
      values: { 1: 'active', 0: 'inactive' }
    }
  },
  unitMapping: {
    age: { asNumber: true }
  },
  pick: ['name', 'age', 'statusLabel']
}

// Result
[
  { name: 'John', age: 20, statusLabel: 'active' }
]