Lodash multi get (with `[]` path syntax)

multiGet.js

const _ = require('lodash');

function multiGet(object, path, defaultValue) {
  return path
    .split('[]')
    .reduce((resolvedPaths, pathShard, pathShardIndex, pathShards) => {
      const isFirstPathShard = pathShardIndex === 0;
      const isLastPathShard = pathShardIndex === pathShards.length -1;
      return resolvedPaths
        .map(resolvedPath => {
          const iterable = (resolvedPath || (pathShard && !isLastPathShard)) ? _.get(object, resolvedPath || pathShard) : object;
          if (typeof iterable !== 'object') {
            throw new Error('Given path does not match object structure.');
          }

          if (!Array.isArray(iterable) || pathShard.startsWith('[')) {
            return [`${resolvedPath}${pathShard}`];
          }

          return iterable.map((e, i) => isFirstPathShard ? `${resolvedPath}${pathShard}[${i}]` : `${resolvedPath}[${i}]${pathShard}`);
        })
        .reduce((a, b) => a.concat(b))
      ;
    }, [''])
    .map(resolvedPath => _.get(object, resolvedPath, defaultValue))
  ;
}

console.log(
  multiGet(
    [
      {
        a: [
          {
            a: true,
          },
          {
            a: true,
          },
        ],
      },
      {
        a: [
          {
            a: true,
          },
          {
            b: true,
          },
        ],
      },
    ], 
    '[1].a[].a', 
    false
  )
);

console.log(
  multiGet(
    {
      a: [
        {
          a: true,
        },
        {
          a: true,
        },
      ],
    }, 
    'a[].a'
  )
);