Is there any function in ramda how can I find key by nested key value? I found a way how to find an object in array but that doesn't help. I need something like this:

const obj = {
  addCompany: {
    mutationId: '1'
  },
  addUser: {
    mutationId: '2'
  },
  addCompany: {
    mutationId: '3'
  }
}
const findByMutationId = R.???
findByMutationId('2', obj) // returns addUser

Is there any function in ramda how can I find key by nested key value? I found a way how to find an object in array but that doesn't help. I need something like this:

const obj = {
  addCompany: {
    mutationId: '1'
  },
  addUser: {
    mutationId: '2'
  },
  addCompany: {
    mutationId: '3'
  }
}
const findByMutationId = R.???
findByMutationId('2', obj) // returns addUser

• javascript
• functional-programming
• ramda.js

4 Answers 4

find bined with propEq and keys should work

const obj = {
  addCompany: {
    mutationId: '1'
  },
  addUser: {
    mutationId: '2'
  },
  addCompany2: {
    mutationId: '3'
  }
}
const findByMutationId = id => obj => R.find(
  R.o(R.propEq('mutationId', id), R.flip(R.prop)(obj)),
  R.keys(obj)
)

console.log(findByMutationId('2')(obj))

<script src="//cdnjs.cloudflare./ajax/libs/ramda/0.24.1/ramda.min.js"></script>

Pointfree versions for the lulz

const obj = {
  addUser: {
    mutationId: '2'
  },
  addCompany: {
    mutationId: '3'
  }
}

const findByMutationId = R.pose(
  R.o(R.head),
  R.o(R.__, R.toPairs),
  R.find,
  R.o(R.__, R.nth(1)),
  R.propEq('mutationId')
)

console.log(findByMutationId('2')(obj))

const findByMutationId2 = R.pose(
  R.ap(R.__, R.keys),
  R.o(R.find),
  R.o(R.__, R.flip(R.prop)),
  R.o,
  R.propEq('mutationId')
)

console.log(findByMutationId2('3')(obj))

<script src="//cdnjs.cloudflare./ajax/libs/ramda/0.24.1/ramda.min.js"></script>

Not sure about ramda, but if a one-liner in plain js is good for you, the following will work

const obj = {
    addCompany: {
        mutationId: '1'
    },
    addUser: {
        mutationId: '2'
    }
};

let found = Object.keys(obj).find(e => obj[e].mutationId === '2');
console.log(found);

If you are gona use this then you might have to polyfill entries, this is good if you need both the key and the value

const obj = {
  addCompany: {
    mutationId: '1'
  },
  addUser: {
    mutationId: '2'
  },
  addCompany: {
    mutationId: '3'
  }
}

let [key, val] = Object.entries(obj).find(obj => obj[1].mutationId == '2')

console.log(key)
console.log(val)

A bit late to the party but better late than never. You could also wrap some of the functions in curry() if you want to make them more posable in the future.

const obj = {
  addCompany: {
    mutationId: '1'
  },
  addUser: {
    mutationId: '2'
  },
  addCompany: {
    mutationId: '3'
  }
}

// search key in obj, where a value satisfies pred
const findObjKey = pred =>
  pipe(
    toPairs,
    find(pose(pred, nth(1))),
    nth(0)
  )

const findByMutationId = (id, obj) => findObjKey(propEq('mutationId', id))(obj)

const res = findByMutationId('2', obj)
console.log(res)