const firstObject = { sampleData: 'Hello world' }const secondObject = { moreData: 'foo bar' }const finalObject = { secondObject, __key: "a key", __src: "a src",};const firstObject = { __key: "a key", __src: "a src", }const secondObject = { moreData: 'foo bar' }const finalObject = Object.assign(firstObject, secondObject);const firstObject = { __key: "a key", __src: "a src", }const secondObject = { moreData: 'foo bar' }const finalObject = { secondObject, firstObject};const __key = "a key";const __src = "a src";const secondObject = { moreData: 'foo bar' }const finalObject = { secondObject, __key, __src,};const __key = "a key";const __src = "a src";const data = { moreData: 'foo bar' }const finalObject = { data, __key, __src,};--enable-precise-memory-info flag.
| Test case name | Result |
|---|---|
| Using the spread operator with constant inside | |
| Using Object.assign to merge two objects | |
| Using the spread operator to merge two objects | |
| Using the spread operator with two extra variables | |
| Composing objects into new one |
| Test name | Executions per second |
|---|---|
| Using the spread operator with constant inside | 63406088.0 Ops/sec |
| Using Object.assign to merge two objects | 8271973.0 Ops/sec |
| Using the spread operator to merge two objects | 19185654.0 Ops/sec |
| Using the spread operator with two extra variables | 58530804.0 Ops/sec |
| Composing objects into new one | 139970288.0 Ops/sec |
Measuring JavaScript performance is crucial for web development, and tools like MeasureThat.net help optimize code for better user experience.
The provided benchmark tests the performance of three different methods to merge objects in JavaScript: using the spread operator (...), Object.assign(), and combining two spreads (...firstObject, ...secondObject). Here's a breakdown of each approach:
1. Using the spread operator (...)
The spread operator is a shorthand way to create a new object with the properties of an existing object. In this benchmark, it's used to merge objects by spreading one object into another.
Pros: Easy to read and write, concise syntax. Cons: Can lead to unexpected behavior if not used carefully (e.g., when dealing with nested objects).
Example code:
const finalObject = { ...secondObject, __key: "a key", __src: "a src" };
2. Using Object.assign()
Object.assign() is a method that copies properties from one or more source objects to a target object.
Pros: Well-documented and widely supported, can handle nested objects. Cons: Can be slower than the spread operator for simple merges.
Example code:
const finalObject = Object.assign({}, secondObject, { __key: "a key", __src: "a src" });
3. Combining two spreads (...firstObject, ...secondObject)
This approach is similar to using the spread operator but combines both objects into a single merge.
Pros: Easy to read and write, can handle nested objects. Cons: Less concise than using the spread operator alone.
Example code:
const finalObject = { ...secondObject, ...firstObject };
The benchmark results show that:
__key and __src) is the fastest (approximately 5-6 times faster than the other approaches).Object.assign() is the slowest of the three methods.Other alternatives to consider:
merge() method: This utility library provides a convenient way to merge objects, handling various scenarios and edge cases. However, it adds an extra dependency to your project....rest): This feature can be used to merge objects by creating a new object with the properties of another object and additional properties from a third object. However, its usage is less common compared to the spread operator.When choosing a method for merging objects in JavaScript, consider factors like performance, readability, and maintainability.
