Create array conditionally (Javascript)

Question

How do we extract the specific field's value from the array (I want to extract id value)

[
    {id:1, added: true, name: 'Book'}, -> I want to extract id value!
    {id:2, added: true, name: 'Desk'},
    {id:5, added: true, name: 'Rock'},
    {id:3, added: false, name: 'Rock'},
    {id:7, added: false, name: 'Rock'},
    {id:8, added: false, name: 'Rock'},
]

and create an array with the values. (only if the added field is true)

Expected Output will be [1, 2, 5].

It will be great if we can catch the edge case when we are getting [] empty array.

Please feel free to use lodash (if it's faster and simple than vanila javascript)

Suren Srapyan · Accepted Answer · 2017-12-03 10:59:26Z

3

You just can use Array#filter combined with Array#map function

const arr = [
    {id:1, added: true, name: 'Book'},
    {id:2, added: true, name: 'Desk'},
    {id:5, added: true, name: 'Rock'},
    {id:3, added: false, name: 'Rock'},
    {id:7, added: false, name: 'Rock'},
    {id:8, added: false, name: 'Rock'},
];

const mappedArr = arr.filter(item => item.added).map(item => item.id);

console.log(mappedArr);

edited Dec 3, 2017 at 10:59

answered Dec 3, 2017 at 10:08

Suren Srapyan

68.9k14 gold badges128 silver badges119 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

merry-go-round Over a year ago

Sorry for replying it late. But can we do this conditionally???? Sorry, I edited the question. I think you can solve it like a charm. Thanks

Ingo Bürk Over a year ago

Add Array#filter first.

Gruff Bunny · Accepted Answer · 2017-12-03 11:16:05Z

3

First filter out the items that have added as false then map across the result to get the id:

let result = _(data)
    .filter('added')
    .map('id')
    .value();

answered Dec 3, 2017 at 11:16

Gruff Bunny

28k10 gold badges74 silver badges61 bronze badges

Comments

Александр Буклей · Accepted Answer · 2017-12-03 11:02:42Z

1

const arr = [
    {id:1, added: true, name: 'Book'},
    {id:2, added: true, name: 'Desk'},
    {id:5, added: true, name: 'Rock'},
    {id:3, added: false, name: 'Rock'},
    {id:7, added: false, name: 'Rock'},
    {id:8, added: false, name: 'Rock'},
];

arr.reduce((prev, curr) => {
    if (curr.added) {
        return [...prev, curr.id];
    }

    return prev;
}, []);

answered Dec 3, 2017 at 11:02

Александр Буклей

315 bronze badges

Comments

Hassan Imam · Accepted Answer · 2017-12-03 11:05:42Z

1

You can use array#reduce and check for the added property, if it is true add the id to accumulator.

var data = [ {id:1, added: true, name: 'Book'}, {id:2, added: true, name: 'Desk'}, {id:5, added: true, name: 'Rock'}, {id:3, added: false, name: 'Rock'}, {id:7, added: false, name: 'Rock'}, {id:8, added: false, name: 'Rock'}],
    result = data.reduce((r, {id, added}) => {
      if(added)
        r.push(id);
      return r;
    }, []); 
console.log(result);

answered Dec 3, 2017 at 11:05

Hassan Imam

22.6k6 gold badges45 silver badges53 bronze badges

Collectives™ on Stack Overflow

Create array conditionally (Javascript)

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related