Graph data by sequential prop

graph-by.js

// Given a list with data containing sequential property such as year of birth, age, size
// Create a graph containing elements groupped by that property with ids of next nodes

// Output example
{
    '1': {list: [{size: 1}, {size: 1}], previous: undefined, next: '3'},
    '3': {list: [{size: 3}], previous: '1', next: '4'},
    '4': {list: [{size: 4}], previous: '3', next: undefined},
}

const graphBy = (items, seqeuentialProp) => {
    const groupped = items.reduce((acc, elem) => {
        if (!(elem[seqeuentialProp] in acc)) {acc[elem[seqeuentialProp]] = {list: []}}
        acc[elem[seqeuentialProp]].list.push(elem)
        return acc;
    }, {});
    const sorted = Object.keys(groupped).sort((a, b) => parseInt(a) - parseInt(b))
    
    sorted.forEach((prop, index) => {
        const prev = sorted[index - 1];
        const next = sorted[index + 1];
        Object.assign(groupped[prop], {prev, next});
    });

    return groupped;
}