creating a new array from two arrays with a new attribute

Question

I have two arrays. First array is an array of object with each object respresenting a vote for an item, the id represents the item that was voted.

The second array contains all the options for that poll.

I want to create a new array with each option from the poll options with a new attribute having the percentage of votes they got from the votes array.

This is the votes array.

votes = [{ 
 vote_id: 1, person: {name: ‘alan’}
}, {
 vote_id: 2, person: {name: ‘John’}
},{ 
 vote_id: 1, person: {name: ‘khan’}
}, { 
vote_id: 1,  person: {name: ‘martin’}
},{ 
vote_id: 3, person: {name: ‘mike’}
}]

Options = [{
id: 1, title: ’sweet’}, {
id: 2: ’salty’}, {
id: 3, title: ’spicy’}, {
id: 4, title: ’bitter’}]

This is the new array that I want to create from the data available from the above two arrays

new array = [{
Id: 1, title: ’sugar’, percentage: 60%},
{Id: 2, title: ’salt’, percentage: 20% },
{id: 3, title: ’spice’, percentage: 20%},
{id: 4, title: ‘bitter’, percentage: 0%}]

Nina Scholz · Accepted Answer · 2022-07-28 17:14:39Z

2

Separate the problem into two parts:

get the counts,
map percentage.

const
    votes = [{ vote_id: 1, person: { name: 'alan' } }, { vote_id: 2, person: { name: 'John' } }, { vote_id: 1, person: { name: 'khan' } }, { vote_id: 1, person: { name: 'martin' } }, { vote_id: 3, person: { name: 'mike' } }],
    options = [{ id: 1, title: 'sweet' }, { id: 2, title: 'salty' }, { id: 3, title: 'spicy' }, { id: 4, title: 'bitter' }],
    counts = votes.reduce((r, { vote_id }) => {
        r[vote_id] = (r[vote_id] || 0) + 1;
        return r;
    }, {}),
    result = options.map(o => ({ ...o, percentage: ((counts[o.id] || 0) * 100 / votes.length).toString() + ' %' }));

console.log(result);

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

edited Jul 28, 2022 at 17:14

answered Jul 28, 2022 at 17:00

Nina Scholz

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1 Comment

kibakoriasu Over a year ago

there's a slight modification in the question, can you please adjust the solution according to the modification

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