CFP - Docs - mSetAtPath

mSetAtPath

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

Set a deep property

Try It

const obj = {
  a: {
    b: 'c',
  },
}
const setBToD = mSetAtPath(['a', 'b'], 'd')
const mutatedObj = setBToD(obj)

console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: {
//     b: 'd'
//   }
// }
const obj = {
  a: {
    b: 'c',
  },
}
const setBToD = mSetAtPath(['a', 'b'], 'd')
const mutatedObj = setBToD(obj)

console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: {
//     b: 'd'
//   }
// }

Try It

const obj = {
  a: {
    b: 'c',
  },
}
const setBToD = mSetAtPath(['a', 'b'], 'd')
const mutatedObj = setBToD(obj)

console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: {
//     b: 'd'
//   }
// }
const obj = {
  a: {
    b: 'c',
  },
}
const setBToD = mSetAtPath(['a', 'b'], 'd')
const mutatedObj = setBToD(obj)

console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: {
//     b: 'd'
//   }
// }

Sometimes we want to set a deep property. Below, we built a website allowing users to choose between light and dark modes. Let's set the account preference to dark.

Try It

const account = {
  email: 'meg@example.com',
  preferences: {
    mode: 'light',
  },
}

const setDarkMode = mSetAtPath(['preferences', 'mode'], 'dark')
setDarkMode(account)

console.log(account)
// is {
//   email: meg@example.com
//   preferences: {
//     mode: dark
//   }
// }
type Account = {
  email: string
  preferences: { mode: string }
}
const account: Account = {
  email: 'meg@example.com',
  preferences: {
    mode: 'light',
  },
}

const setDarkMode = mSetAtPath(['preferences', 'mode'], 'dark')<Account>
setDarkMode(account)

console.log(account)
// is {
//   email: meg@example.com
//   preferences: {
//     mode: dark
//   }
// }

Try It

const account = {
  email: 'meg@example.com',
  preferences: {
    mode: 'light',
  },
}

const setDarkMode = mSetAtPath(
  ['preferences', 'mode'],
  'dark'
)
setDarkMode(account)

console.log(account)
// is {
//   email: meg@example.com
//   preferences: {
//     mode: dark
//   }
// }
type Account = {
  email: string
  preferences: { mode: string }
}
const account: Account = {
  email: 'meg@example.com',
  preferences: {
    mode: 'light',
  },
}

const setDarkMode = mSetAtPath(
  ['preferences', 'mode'],
  'dark'
)<Account>
setDarkMode(account)

console.log(account)
// is {
//   email: meg@example.com
//   preferences: {
//     mode: dark
//   }
// }

This utility has a few requirements

Path must have at least one element
Path must exist on the object and be assignable

The example shows the errors thrown for each requirement

Try It

try {
  mSetAtPath([], 'path cannot be empty')
} catch (err) {
  console.log(err)
  // prints
  // mSetAtPath requries 'path' to be a non-empty array
}

const setBToD = mSetAtPath(['a', 'b'], 'd')

try {
  const noA = {}
  setBToD(noA)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires path to exist on 'anything'.  Arguments are assigned to
  // this error to aid in debugging.
}

try {
  const bIsUnassignable = { a: "can't assign a property to primitive" }
  setBToD(bIsUnassignable)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires the property at path to be assignable.  See error
  // properties for more info.
}
try {
  mSetAtPath([], 'path cannot be empty')
} catch (err) {
  console.log(err)
  // prints
  // mSetAtPath requries 'path' to be a non-empty array
}

const setBToD = mSetAtPath(['a', 'b'], 'd')

try {
  const noA = {}
  setBToD(noA)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires path to exist on 'anything'.  Arguments are assigned to
  // this error to aid in debugging.
}

try {
  const bIsUnassignable = { a: "can't assign a property to primitive" }
  setBToD(bIsUnassignable)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires the property at path to be assignable.  See error
  // properties for more info.
}

Try It

try {
  mSetAtPath([], 'path cannot be empty')
} catch (err) {
  console.log(err)
  // prints
  // mSetAtPath requries 'path' to be a non-empty
  // array
}

const setBToD = mSetAtPath(['a', 'b'], 'd')

try {
  const noA = {}
  setBToD(noA)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires path to exist on
  // 'anything'.  Arguments are assigned to this
  // error to aid in debugging.
}

try {
  const bIsUnassignable = {
    a: "can't assign a property to primitive",
  }
  setBToD(bIsUnassignable)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires the property at path to
  // be assignable.  See error properties for
  // more info.
}
try {
  mSetAtPath([], 'path cannot be empty')
} catch (err) {
  console.log(err)
  // prints
  // mSetAtPath requries 'path' to be a non-empty
  // array
}

const setBToD = mSetAtPath(['a', 'b'], 'd')

try {
  const noA = {}
  setBToD(noA)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires path to exist on
  // 'anything'.  Arguments are assigned to this
  // error to aid in debugging.
}

try {
  const bIsUnassignable = {
    a: "can't assign a property to primitive",
  }
  setBToD(bIsUnassignable)
} catch (err) {
  console.log('\n', err)
  // prints
  // mSetAtPath requires the property at path to
  // be assignable.  See error properties for
  // more info.
}