"pickBy" the value in the value array of an object

Question

I have an object that looks like:

let documents = {"A": [{"document":"test1", "serial":"123"}, {"document":"test2", "serial":"456N"}], "B": [{"document":"test3", "serial":"789N"}, {"document":"test24, "serial":"012"}]};

I was trying to get a filtered object that has serial number ending with "N":

{"A": [{"document":"test2", "serial":"456N"}, "B": [{"document":"test3", "serial":"789N"}]}

I was doing:

 let result = _.pickBy(documents, (docObjs, client) => {
       return _.filter(docObjs, ({serial}) => {
         return _.endsWith(serial, 'N');
       });
 });

But what I got was the original object (same as documents). Is there anything wrong?

Answer 1

Lodash

Iterate the client's object with _.transform(). For each client, filter the list of documents using _.endsWith(). If the list of documents is not empty (length 0), assign the client with filtered docs list to the result object:

// added client C that will be filtered out
const documents = {"A": [{"document":"test1", "serial":"123"}, {"document":"test2", "serial":"456N"}], "B": [{"document":"test3", "serial":"789N"}, {"document":"test24", "serial":"012"}], "C": [{"document":"test25", "serial":"013"}]};

const result = _.transform(documents, (r, v, k) => {
  const docs = _.filter(v, ({ serial }) => _.endsWith(serial, 'N'));
  if(!_.isEmpty(docs)) r[k] = docs;
});

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

Vanilla JS

Get an array of client/document pairs with Object.entries(). Using Array.map() and Array.filter() remove all documents with serials that don't String.endsWith() the letter N. Use Array.filter() to remove all entries with 0 documents. Convert back to an object using Array.reduce():

// added client C that will be filtered out
const documents = {"A": [{"document":"test1", "serial":"123"}, {"document":"test2", "serial":"456N"}], "B": [{"document":"test3", "serial":"789N"}, {"document":"test24", "serial":"012"}], "C": [{"document":"test25", "serial":"013"}]};

const result = Object.entries(documents)
  // filter the least of documents in each client entry
  .map(([k, v]) => [k, v.filter(({ serial }) => serial.endsWith('N'))])
  // filter clients that have 0 documents
  .filter(([k, v]) => v.length)
  // convert back to an object
  .reduce((r, [k, v]) => (r[k] = v, r), {});

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>