Compare values in 2 object arrays and create new array, js

Question

I have 2 arrays:

blockedNumbers: ['123', '456', '789', '247'];
contacts: [
           {name: 'Foo', numbers: [{ home:'123' }, { mobile:'456' }]}, 
           {name: 'Bar', numbers: [{ home:'789' }]}
          ]

I want to create a new array of blocked contacts which will contain:

[
  { name: Foo, numbers: [{ home:'123' }, { mobile:'456' }] }, 
  {name: 'Bar', numbers: [{ home:'789' }]} 
  '247'
]

So the solution I have tried first loops over blocked numbers, then forEach contact, if blocked number in numbers, push to array. But the result turns out as

[
  '123'
  { name: Foo, numbers: ['123', '456'] }, 
  {name: 'Bar', numbers: ['789']} 
  '456'
  '789'
  '247'
]

Code below:

const newBlacklistWithContacts = [];
blockedNumbers.forEach((blockedNumber) => {
    contacts.map((contact) => {
    // if blocked number in contacts
    Object.keys(contact.numbers).forEach((e) => {
    if (contact.numbers[e] === blockedNumber) {
        const alreadyAdded = newBlacklistWithContacts.find(blacklistContact => blacklistContact.name === contact.name);
        if (!alreadyAdded) {
            return newBlacklistWithContacts.push({ name: contact.name, numbers: contact.numbers });
        }
    }
    else if (!newBlacklistWithContacts.includes(blockedNumber)) {
        return newBlacklistWithContacts.push(blockedNumber);
    }
    });
    });
});

I'm sure there is a more efficient way to do this & actually return what I need? (All of the blacklisted contacts and if not in contacts, only the number) I am using js and React.js in this project

trincot · Accepted Answer · 2018-08-07 12:32:52Z

4

If your data set is really large, you can optimise your algorithm by doing O(1) lookups in a Set instead of using indexOf or includes which do O(n) lookups:

// Input
const blockedNumbers =  ['123', '456', '789', '247'];
const contacts = [{name: 'Foo', numbers: [{ home:'123' }, { mobile:'456' }]}, {name: 'Bar', numbers: [{ home:'789' }]}];

// Algorithm
const set = new Set(blockedNumbers);
const notused = new Set(blockedNumbers);
const newBlacklistWithContacts = contacts.filter(contact => 
    contact.numbers.map(obj => Object.values(obj)[0])
                   .filter(number => set.has(number) && (notused.delete(number) || true)).length
).concat(...notused);

// Output
console.log(newBlacklistWithContacts);

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

answered Aug 7, 2018 at 12:32

trincot

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Comments

Nishant Dixit · Accepted Answer · 2018-08-07 12:25:34Z

0

var blockedNumbers = ['123', '456', '789', '247'];
var contacts = [{
        name: 'Foo',
        numbers: [{
            home: '123'
        }, {
            mobile: '456'
        }]
    },
    {
        name: 'Bar',
        numbers: [{
            home: '789'
        }]
    }
]

var blocks = [];
contacts.forEach(v1 => (v1.numbers.forEach(v2 => {
    blocks.push(Object.values(v2)[0]);
})));
blockedNumbers.forEach(val => (blocks.indexOf(val) == -1 ? contacts.push(val) : null));

console.log(contacts);

answered Aug 7, 2018 at 12:25

Nishant Dixit

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1 Comment

trincot Over a year ago

Two issues: (1) This mutates the input. (2) This always includes all contacts, not just the blacklisted.

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