Group array of object nesting some of the keys with specific names

Question

I have this array of objects, that I need to modify to make it easier the rendering.

const items = [
  {
    tab: \'Results\',
    section: \'2017\',
    ti         


        

Answer 1

This can be done with a clever combinartion of _.map and _.groupBy.

const items = [
  {
    tab: 'Results',
    section: '2017',
    title: 'Full year Results',
    description: 'Something here',
  },
    {
    tab: 'Results',
    section: '2017',
    title: 'Half year Results',
    description: 'Something here',
  },
    {
    tab: 'Reports',
    section: 'Marketing',
    title: 'First Report',
    description: 'Something here',
  }
];

function groupAndMap(items, itemKey, childKey, predic){
    return _.map(_.groupBy(items,itemKey), (obj,key) => ({
        [itemKey]: key,
        [childKey]: (predic && predic(obj)) || obj
    }));
}

var result = groupAndMap(items,"tab","sections", 
                   arr => groupAndMap(arr,"section", "items"));


console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Answer 2

You could use an object without additional libraries.

The object contains a property _ which keeps the nested arrays of the given nested group.

var items = [{ tab: 'Results', section: '2017', title: 'Full year Results', description: 'Something here' }, { tab: 'Results', section: '2017', title: 'Half year Results', description: 'Something here' }, { tab: 'Reports', section: 'Marketing', title: 'First Report', description: 'Something here' }],
    keys = { tab: 'sections', section: 'items' }, // or more if required
    result = [],
    temp = { _: result };

items.forEach(function (object) {
    Object.keys(keys).reduce(function (level, key) {
        if (!level[object[key]]) {
            level[object[key]] = { _: [] };
            level._.push({ [key]: object[key], [keys[key]]: level[object[key]]._ });
        }
        return level[object[key]];
    }, temp)._.push({ title: object.title, description: object.description });
});

console.log(result);

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