node.js - Make array of flattened out value from nested array object in Javascript

Question

I have the following array object.

    let reports = [
        {
            cc: 'BEL',
            cn: 'Belgium',
            entities: [
                {
                    entityName: 'Company A',
                    address: 'some address'
                }, 
                {
                    entityName: 'Company B',
                    address: 'some address'
                }
            ]
        },
        {
            cc: 'LUX',
            cn: 'Luxembourg',
            entities: [
                {
                    entityName: 'Company C',
                    address: 'some address'
                }
            ]
        }
    ];

I want to go through reports and create a new array with only the value of entityName how can I accomplish this?

The new array should look like ['Company A', 'Company B', 'Company C']. How can I accomplish this?

I tried doing: reports.map(e => e.entities.map(r => r.entityName)). However this returns:

[['Company A', 'Company B'], ['Company C']]

question from:https://stackoverflow.com/questions/65936297/make-array-of-flattened-out-value-from-nested-array-object-in-javascript

Answer 1

You can use .flat() on your result.

let reports = [
        {
            cc: 'BEL',
            cn: 'Belgium',
            entities: [
                {
                    entityName: 'Company A',
                    address: 'some address'
                }, 
                {
                    entityName: 'Company B',
                    address: 'some address'
                }
            ]
        },
        {
            cc: 'LUX',
            cn: 'Luxembourg',
            entities: [
                {
                    entityName: 'Company C',
                    address: 'some address'
                }
            ]
        }
    ];




const res = reports.map(e => e.entities.map(r => r.entityName)).flat();
console.log(res);