how to update a property in JSON array - Ramdajs

Question

Input:

[{
    message: 'A1 Message, B1 Message, C1 Message'
}, {
    message: 'A1 Message, B1 Message'
}];

Output:

[{
    message: 'C1 Message'
}, {
    message: null
}];

Identify a particular message "C1" (substring) and update the string or set to null in array of objects

Tried the below:

var input = [{
    id: 1,
    message: 'A1 Message, B1 Message, C1 Message'
}, {
    id: 2,
    message: 'A1 Message, B1 Message'
}];

var updateMessage = (obj) => {
    var C1Message = R.pipe(
        R.prop('message'),
        R.splitAt(obj.message.indexOf('C1')),
        R.last
    )(obj);
    return R.assoc('message', C1Message, obj);
}

var updateArray = R.map(R.when(R.pipe(R.prop('message'), R.includes('C1')), updateMessage));
var output = updateArray(input);
console.log(output);

How to use ifElse to set the second object message as null?

Answer 1

You can evolve the each object in the array. For each message try to match the message format that you need. If no match found (empty array) return null. If a match was found, take the 1st element from the results of R.match:

const { map, evolve, pipe, match, ifElse, isEmpty, always, head } = R

const fn = map(evolve({
  message: pipe(
    match(/C1[^,]+/), // match C1 message
    ifElse(isEmpty, 
      always(null), // if empty assign null
      head // if not take the 1st element
    )
  )
}))

const data = [{ message: 'A1 Message, B1 Message, C1 Message' }, { message: 'A1 Message, B1 Message' }];

const result = fn(data)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.28.0/ramda.min.js" integrity="sha512-t0vPcE8ynwIFovsylwUuLPIbdhDj6fav2prN9fEu/VYBupsmrmk9x43Hvnt+Mgn2h5YPSJOk7PMo9zIeGedD1A==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

Dynamic use - pass the RegExp as a parameter:

const { map, evolve, pipe, match, ifElse, isEmpty, always, join } = R

const fn = regexp => map(evolve({
  message: pipe(
    match(regexp), // match a RegExp
    ifElse(isEmpty, 
      always(null), // if empty assign null
      join(', ') // if not convert to a string
    )
  )
}))

const data = [{ message: 'A1 Message, B1 Message, C1 Message 1, C1 Message 2' }, { message: 'A1 Message, B1 Message' }];

const result = fn(/C1[^,]+/g)(data)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.28.0/ramda.min.js" integrity="sha512-t0vPcE8ynwIFovsylwUuLPIbdhDj6fav2prN9fEu/VYBupsmrmk9x43Hvnt+Mgn2h5YPSJOk7PMo9zIeGedD1A==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>