syntax/support for dynamic paths

[acutmore]

There are at least two situations where needing to specify the path literally can be frustrating:

Situation 1: Mutating deep path based on current value

player = #{
  ...player,
  // 'stats.medals.gold' repeated
  stats.medals.gold: player.stats.medals.gold + 1
}

Situation 2: writing utility function for updating a path

function increment(record, ...path) {
   // even a 'simple' implementation is ~10 lines before adding error checks
   assert(path.length > 0);
   let [prop, ...rest] = path;
   if (rest.length === 0) {
     return {
        ...record,
        [prop]: record[prop] + 1
     }
   }
   return {
     ...record,
     [prop]: increment(record[prop], ...rest)
   }
}

Idea: Add syntax for dynamic paths

If a value could be used as a path then it can be reused and passed around. An array of string/number keys could be used for such a value. Above examples become:

let path = ['stats', 'medals', 'gold'];
player = #{
  ...player,
  [...path]: player[...path] + 1
}

function increment(record, ...path) {
   assert(path.length > 0);
   return #{ ...record, [...path]: record[...path] + 1 }
}

Alternative: Add static helper

Alternatively this type of update could be added to the global Record object. Something like Record.update(record, path, update).

player = Record.update(player, ['stats', 'medals', 'gold'], val => val + 1);

function increment(record, ...path) {
   assert(path.length > 0);
   return Record.update(record, path, val => val + 1);
}