Group By

mediumcodingJavaScriptArraysObjects~25 min

Asked at Google, Meta, Amazon

Overview

Implement groupBy(array, iteratee) — groups elements into arrays keyed by the result of iteratee.

Examples

groupBy([6.1, 4.2, 6.3], Math.floor); // { '4': [4.2], '6': [6.1, 6.3] }

Solution

Reveal solution

function groupBy(array, iteratee) {
  const result = {};
  for (const item of array) {
    const key = String(iteratee(item));
    if (!result[key]) result[key] = [];
    result[key].push(item);
  }
  return result;
}

group-by.js

Group By

mediumcodingJavaScriptArrays

Overview

Implement groupBy(array, iteratee) — groups elements into arrays keyed by the result of iteratee.

Examples

groupBy([6.1, 4.2, 6.3], Math.floor); // { '4': [4.2], '6': [6.1, 6.3] }

Solution

Reveal solution

function groupBy(array, iteratee) {
  const result = {};
  for (const item of array) {
    const key = String(iteratee(item));
    if (!result[key]) result[key] = [];
    result[key].push(item);
  }
  return result;
}

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