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Javascript – Rank an array of objects by category and value

I am working with a large array in the following format:

// Sample data
const array = [
{country: "Germany", category: "A", value: 300},
{country: "Brazil", category: "A", value: 200},
{country: "Canada", category: "A", value: 200},
{country: "Germany", category: "B", value: 100},
{country: "Brazil", category: "B", value: 400},
{country: "Canada", category: "B", value: 500},
]

and I want to want to rank the values by category and value rank and potentially add an overall_rank without considering the category:

// Expected result
[
{country: "Germany", category: "A", value: 300, rank: 1, overall_rank: 2},
{country: "Brazil", category: "A", value: 200, rank: 2, overall_rank: 3},
{country: "Canada", category: "A", value: 200, rank: 2, overall_rank: 3},
{country: "Germany", category: "B", value: 100, rank: 3, overall_rank: 4},
{country: "Brazil", category: "B", value: 200, rank: 2, overall_rank: 3},
{country: "Canada", category: "B", value: 500, rank: 1, overall_rank: 1},
]

So far I got and overall_rank working, but I am struggling ranking the values by value and category:

var overall_rank = 1;
for (var i = 0; i < array.length; i++) {
  if (i > 0 && array[i].value < array[i - 1].value) {
    overall_rank++;
  }
    array[i].overall_rank = overall_rank;
}

How to move forward?

Tags:

2

Answers


  1. 0

    To get the rank within the category, you can first use Object.groupBy to split the objects based on their category property, then sort each of the categories separately.

    const array = [
  {country: "Germany", category: "A", value: 300},
  {country: "Brazil", category: "A", value: 200},
  {country: "Canada", category: "A", value: 200},
  {country: "Germany", category: "B", value: 100},
  {country: "Brazil", category: "B", value: 400},
  {country: "Canada", category: "B", value: 500},
];
for (const category of Object.values(Object.groupBy(array, o => o.category))) {
  let i = 0, prev;
  for (const o of category.sort((a, b) => b.value - a.value)) {
    o.rank = i += prev !== o.value;
    prev = o.value;
  }
}
console.log(array);
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  2. 0

    You could sort each record and assign a unique rank:

    const arr = [
  { country: "Germany", category: "A", value: 300 },
  { country: "Brazil",  category: "A", value: 200 },
  { country: "Canada",  category: "A", value: 200 },
  { country: "Germany", category: "B", value: 100 },
  { country: "Brazil",  category: "B", value: 400 },
  { country: "Canada",  category: "B", value: 500 },
];

const sorted = arr.toSorted((a, b) =>
  b.value - a.value ||
  a.category?.localeCompare(b.category) ||
  a.country?.localeCompare(b.country)) ||
  0;

const result = arr.map((record) => ({
  ...record,
  overall_rank: sorted.indexOf(record) + 1
}));

console.log(...result.map(JSON.stringify));
    .as-console-wrapper { top: 0; max-height: 100% !important; }

    Or you could group by value:

    const arr = [
  { country: "Germany", category: "A", value: 300 },
  { country: "Brazil",  category: "A", value: 200 },
  { country: "Canada",  category: "A", value: 200 },
  { country: "Germany", category: "B", value: 100 },
  { country: "Brazil",  category: "B", value: 400 },
  { country: "Canada",  category: "B", value: 500 },
];

const grouped = [...arr
  .reduce((acc, record, index) =>
    acc.set(record.value, [...(acc.get(record.value) ?? []), record]),
    new Map())
  .entries()]
  .sort(([a], [b]) => b - a);
  
const result = arr.map((record) => ({
  ...record,
  overall_rank: grouped.findIndex(([value]) => value === record.value) + 1
}));

console.log(...result.map(JSON.stringify));
    .as-console-wrapper { top: 0; max-height: 100% !important; }
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