How Can I Efficiently Merge JavaScript Objects by ID Using ES6?

Merging JavaScript Objects by ID: A Comprehensive Guide

Merging objects by an identifier (id) is a common task in JavaScript programming, especially when combining data from different sources. This guide will present an efficient solution using a concise ES6 syntax.

Solution:

To merge two arrays of objects based on the id field, we can use the following approach:

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

Explanation:

• The map() method iterates over the first array (a1).
• For each object t1 in a1, we create a new object using the spread operator (...) to copy its properties.
• We use find() on the second array (a2) to search for an object with a matching id to t1.
• The found object's properties are then copied into the new object using the spread operator.

Example Usage:

Consider the example arrays provided in the question:

var a1 = [{ id: 1, name: "test"}, { id: 2, name: "test2"}];
var a2 = [{ id: 1, count: "1"}, {id: 2, count: "2"}];

Applying the above solution will produce the desired merged array:

var a3 = [{ id: 1, name: "test", count: "1"}, 
          { id: 2, name: "test2", count: "2"}];

Advantages:

• Concise and readable code.
• Efficient use of ES6 spread operator for object merging.
• Handles both existing and missing properties in the merged objects.

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