How Can I Efficiently Merge JavaScript Objects Based on an ID Field?

Merging Objects in JavaScript Based on Id Field

Combining data from multiple arrays is a common task in JavaScript development. When dealing with arrays containing objects, it becomes necessary to merge them based on a specific field, such as the "id" field.

To merge arrays of objects based on the "id" field, a powerful approach using the ES6 spread operator can be employed:

const a3 = a1.map((t1) => ({
  ...t1,
  ...a2.find((t2) => t2.id === t1.id),
}));

In this snippet:

• a1 and a2 represent the input arrays to be merged.
• The map() method iterates over each item in a1.
• For each item t1 in a1, an anonymous arrow function is executed.
• Within the arrow function, the spread operator (...) is used to create a new object.
• The first set of dots merges the properties of t1, retaining the original values.
• The second set of dots merges the properties of an element found in a2 that has the same "id" as t1. The find() method searches a2 for a match.
• The resulting a3 array contains the merged objects.

Using this approach, the "count" property is added to the existing "name" property of each object in the merged array a3. This technique can be extended to merge objects based on any desired field, providing a concise and efficient way to combine data in JavaScript.

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