alias-mapper

A small utility for mapping aliases in JavaScript/Typescript objects.

Usage

alias-mapper provides two types of alias mapping:

Composite Aliases

Map source keys to a composite target object:

import { compositeAliases } from 'alias-mapper'

const { build } = compositeAliases({
  center: {
    _aliases: ['c'],
    x: 'center',
    y: 'middle'
  }
})

const source = {
  c: true
}

const result = build(source) // -> { x: 'center', y: 'middle' }

You can also compute a value with compositeAliases using _compute. In a single alias, normal key-values can be used together with _compute, but note that _compute is executed after the entire map has been computed. This way you can target the already generated static mapping results in your computation function.

const comp = compositeAliases({
  color: {
    _aliases: ['c'],
    _compute: (value, context) => { // parse colors like '#ff0000' or 'rgb(255, 0, 0)'
      if (value.startsWith('rgb(')) {
        const [r, g, b] = value.slice(4, -1).split(',').map(Number)
        return { color: { r, g, b } }
      } else if (value.startsWith('#')) {
        const r = parseInt(value.slice(1, 3), 16)
        const g = parseInt(value.slice(3, 5), 16)
        const b = parseInt(value.slice(5, 7), 16)
        return { color: { r, g, b } }
      }
      return {}
    }
  }
})

comp.build({ c: '#ff0000' }) // -> { color: { r: 255, g: 0, b: 0 }}

Key-Value Aliases

Map source keys/values to aliased target keys/values:

import { keyValueAliases } from 'alias-mapper'

const { build } = keyValueAliases({
  firstName: {
    _aliases: ['fn'],
  },
  status: {
    active: ['a'],
    inactive: ['i']
  }
})

const source = {
  fn: 'John',
  s: 'a'  
}

const result = build(source)

// result
{
  firstName: 'John'
  status: 'active'
}

Cast your types in key-value maps (> 1.0.3)

The _castTo feature was added in version 1.0.3. This feature allows you to specify the type to which a value should be cast when applying key-value aliases. You can do this by adding an optional _castTo field to the alias map object for a given key.

The _castTo field can take the values boolean or number, indicating that the value should be cast to a boolean or a number, respectively.

Boolean example:

interface Switch {
  enabled: boolean
}

const kv = keyValueAliases<Switch>({
  enabled: {
    _aliases: ['status'],
    _castTo: 'boolean',
    true: ['on'],
    false: ['off']
  }
})

const result = kv.build({ status: 'on' })

// result
{
  enabled: true
}

The check is for a match with true in any regex. So if the conversion is impossible, the result will be false.

Number example:

interface Counter {
  value: number
}

const kv = keyValueAliases<Counter>({
  value: {
    _castTo: 'number',
    0: ['reset']
  }
})

const result = kv.build({ value: '5' })
// result
{
  value: 5
}

const result2 = kv.build({ value: 'reset' })
{
  value: 0
}

Casting to number uses the built-in Number() constructor. So if conversion is not possible, the value will be NaN.

Typescript support

You can improve your development experience by using Typescript interfaces as generics to functions. This will give you an autocomplete for more convenient schema completion.

interface Pos {
  x: 'left' | 'center' | 'right',
  y: 'bottom' | 'middle' | 'top'
}

const { build: comp } = compositeAliases<Pos>({
  center: {
    _aliases: ['c'],
    x: 'center', // autocomplete your interface variables
    y: 'middle'
  }
})

const { build: kv } = keyValueAliases<Pos>({
  x: {
    _aliases: ['horizontal'],
    center: ['c'], // autocomplete your enum values
    right: ['r'],
    left: ['l']
  }
})

However, build() will still return any. It is assumed that a library like zod will be used for parsing values.

Contributing

Contributions are welcome! Please open an issue or PR on GitHub.

License

MIT