Data Merging

mediumcodingJavaScriptObjectsArrays~25 min

Asked at Google, Meta, Amazon

Overview

Implement dataMerge(arr1, arr2, key) that merges objects from both arrays matching on key. Properties from arr2 override arr1.

Examples

dataMerge(
  [{ id: 1, name: 'Alice' }],
  [{ id: 1, age: 25 }],
  'id'
); // [{ id: 1, name: 'Alice', age: 25 }]

Solution

Reveal solution

function dataMerge(arr1, arr2, key) {
  const map = new Map();
  for (const item of arr1) map.set(item[key], { ...item });
  for (const item of arr2) {
    const existing = map.get(item[key]) || {};
    map.set(item[key], { ...existing, ...item });
  }
  return Array.from(map.values());
}

data-merging.js

Data Merging

mediumcodingJavaScriptObjects

Overview

Implement dataMerge(arr1, arr2, key) that merges objects from both arrays matching on key. Properties from arr2 override arr1.

Examples

dataMerge(
  [{ id: 1, name: 'Alice' }],
  [{ id: 1, age: 25 }],
  'id'
); // [{ id: 1, name: 'Alice', age: 25 }]

Solution

Reveal solution

function dataMerge(arr1, arr2, key) {
  const map = new Map();
  for (const item of arr1) map.set(item[key], { ...item });
  for (const item of arr2) {
    const existing = map.get(item[key]) || {};
    map.set(item[key], { ...existing, ...item });
  }
  return Array.from(map.values());
}

NameTopicDifficulty

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