CFP - Docs - getAtPath

getAtPath

(path: PropertyKey[]) => (anything: any) => any

Return the value found at path

Try It

const obj = { a: { b: 'c' } }
const getValueAtB = getAtPath(['a', 'b'])
getValueAtB(obj) // is 'c'
getValueAtB({}) // is undefined

const arr = [{ a: 'b' }]
const getValueAtA = getAtPath([0, 'a'])
getValueAtA(arr) // is 'b'
const obj = { a: { b: 'c' } }
const getValueAtB = getAtPath(['a', 'b'])
getValueAtB(obj) // is 'c'
getValueAtB({}) // is undefined

const arr = [{ a: 'b' }]
const getValueAtA = getAtPath([0, 'a'])
getValueAtA(arr) // is 'b'

Try It

const obj = { a: { b: 'c' } }
const getValueAtB = getAtPath(['a', 'b'])
getValueAtB(obj) // is 'c'
getValueAtB({}) // is undefined

const arr = [{ a: 'b' }]
const getValueAtA = getAtPath([0, 'a'])
getValueAtA(arr) // is 'b'
const obj = { a: { b: 'c' } }
const getValueAtB = getAtPath(['a', 'b'])
getValueAtB(obj) // is 'c'
getValueAtB({}) // is undefined

const arr = [{ a: 'b' }]
const getValueAtA = getAtPath([0, 'a'])
getValueAtA(arr) // is 'b'

Sometimes we want to reach a deep property. Below, we have a contact list for our team. We're picking everyone up, and they all live in the area, so let's get everyone's streets.

Try It

const contacts = {
  chris: {
    address: {
      street: '123 Main',
      state: 'Maine',
      zip: '04841',
    },
  },
  liz: {
    address: {
      street: '987 Park',
      state: 'Maine',
      zip: '04841',
    },
  },
  phil: {
    address: {
      street: '555 Oak',
      state: 'Maine',
      zip: '04841',
    },
  },
}

const getStreet = getAtPath(['address', 'street'])
const getAllStreets = mapValues(getStreet)
const streetByPerson = getAllStreets(contacts)
console.log(streetByPerson)
// is {
//   chris: 123 Main
//   liz: 987 Park
//   phil: 555 Oak
// }
type Address = {
  address: {
    street: string
    state: string
    zip: string
  }
}
type Directory = Record<string, Address>
const contacts: Directory = {
  chris: {
    address: {
      street: '123 Main',
      state: 'Maine',
      zip: '04841',
    },
  },
  liz: {
    address: {
      street: '987 Park',
      state: 'Maine',
      zip: '04841',
    },
  },
  phil: {
    address: {
      street: '555 Oak',
      state: 'Maine',
      zip: '04841',
    },
  },
}

const getStreet = getAtPath(['address', 'street'])<Address>
const getAllStreets = mapValues(getStreet)<Directory>
const streetByPerson = getAllStreets(contacts)
console.log(streetByPerson)
// is {
//   chris: 123 Main
//   liz: 987 Park
//   phil: 555 Oak
// }

Try It

const contacts = {
  chris: {
    address: {
      street: '123 Main',
      state: 'Maine',
      zip: '04841',
    },
  },
  liz: {
    address: {
      street: '987 Park',
      state: 'Maine',
      zip: '04841',
    },
  },
  phil: {
    address: {
      street: '555 Oak',
      state: 'Maine',
      zip: '04841',
    },
  },
}

const getStreet = getAtPath(['address', 'street'])
const getAllStreets = mapValues(getStreet)
const streetByPerson = getAllStreets(contacts)
console.log(streetByPerson)
// is {
//   chris: 123 Main
//   liz: 987 Park
//   phil: 555 Oak
// }
type Address = {
  address: {
    street: string
    state: string
    zip: string
  }
}
type Directory = Record<string, Address>
const contacts: Directory = {
  chris: {
    address: {
      street: '123 Main',
      state: 'Maine',
      zip: '04841',
    },
  },
  liz: {
    address: {
      street: '987 Park',
      state: 'Maine',
      zip: '04841',
    },
  },
  phil: {
    address: {
      street: '555 Oak',
      state: 'Maine',
      zip: '04841',
    },
  },
}

const getStreet = getAtPath([
  'address',
  'street',
])<Address>
const getAllStreets = mapValues(
  getStreet
)<Directory>
const streetByPerson = getAllStreets(contacts)
console.log(streetByPerson)
// is {
//   chris: 123 Main
//   liz: 987 Park
//   phil: 555 Oak
// }

When resolving the path, this utility does not treat Maps differently. It only gets object properties.