CODEWITHSUNDEEP
javascriptnode.js
user1513388
user1513388

Reputation: 7441

Splitting an array of arrays

I have an array of arrays that looks like this. 

const data = [
    ['list1'],
    ['item1', '1'],
    ['item2', '2'],
    ['item3', '3'],
    ['item4', '4'],
    [' ']
    ['list2'],
    ['item1', '1'],
    ['item2', '2'],
    ['item3', '3'],
    ['item4', '4'],
    [' ']
    ['list3'],
    ['item1', '1'],
    ['item2', '2'],
    ['item3', '3'],
    ['item4', '4'],
    [' ']
]

I need to get all of the items between the list1, list2 & list3 and the empty value to build a more structured container so that list1, list2 & list3 include the items as children. e.g. {

const data2 = {
    'list1': {'item1': '1', 'item2': '2', 'item3': '3', 'item4': '4'},
    'list2': {'item1': '1', 'item2': '2', 'item3': '3', 'item4': '4'},
    'list3': {'item1': '1', 'item2': '2', 'item3': '3', 'item4': '4'},
    'list4': {'item1': '1', 'item2': '2', 'item3': '3', 'item4': '4'}
}

Whats the most efficient way to query the data array to get the items between the list headers? I see lodash has a _.slice method which takes an index but I can't see a way to use the value of the array as a delimiter.

Upvotes: 1

Views: 68

Answers (2)

Xiaoy312
Xiaoy312

Reputation: 14477

Try this:

const data = [
  ['list1'],
  ['item1', '1'],
  ['item2', '2'],
  ['item3', '3'],
  ['item4', '4'],
  [' '],
  ['list2'],
  ['item1', '1'],
  ['item2', '2'],
  ['item3', '3'],
  ['item4', '4'],
  [' '],
  ['list3'],
  ['item1', '1'],
  ['item2', '2'],
  ['item3', '3'],
  ['item4', '4'],
  [' ']
];

var result = {};
var lastList = null;
for (var item of data) {
  if (item.length == 1 && item[0] != ' ') {
    result[item[0]] = lastList = {};
  }

  else if (lastList != null && item.length == 2) {
    lastList[item[0]] = item[1];
  }
}

console.log(result);

Upvotes: 2

Nina Scholz
Nina Scholz

Reputation: 386604

You could reduce the whole array by using a closure over a reference to the last object with the given key.

var data = [['list1'], ['item1', '1'], ['item2', '2'], ['item3', '3'], ['item4', '4'], [' '], ['list2'], ['item1', '1'], ['item2', '2'], ['item3', '3'], ['item4', '4'], [' '], ['list3'], ['item1', '1'], ['item2', '2'], ['item3', '3'], ['item4', '4'], [' ']],
    result = data.reduce(function (ref) {
        return function (r, a) {
            if (1 in a) {
                ref[a[0]] = a[1];
            } else if (a[0].trim()) {
                r[a[0]] = {};
                ref = r[a[0]]
            }
            return r;
        };
    }(undefined), {});

console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 2

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