const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = {
firstObject,
secondObject
};
const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = Object.assign({}, firstObject, secondObject);
const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = {}
for (let key in firstObject) {
finalObject[key] = firstObject[key];
}
for (let key in secondObject) {
finalObject[key] = secondObject[key];
}
const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = {}
if (firstObject != null) {
for (let key in firstObject) {
finalObject[key] = firstObject[key];
}
}
if (secondObject != null) {
for (let key in secondObject) {
finalObject[key] = secondObject[key];
}
}
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
Using the spread operator | |
Using Object.assign | |
Using For-In loop | |
Using For-In loop with type checks |
Test name | Executions per second |
---|---|
Using the spread operator | 3306413.2 Ops/sec |
Using Object.assign | 4934191.0 Ops/sec |
Using For-In loop | 9874058.0 Ops/sec |
Using For-In loop with type checks | 9721798.0 Ops/sec |
Let's dive into the explanation of the provided benchmark.
Benchmark Overview
The benchmark measures the performance of three different approaches to merge objects without mutation:
...
)Object.assign()
Options Comparison
Here's a brief comparison of the options:
...
operator to create a new object with the properties from both firstObject
and secondObject
. It's a concise and modern way to merge objects.Object.assign()
method to create a new object with the properties from both firstObject
and secondObject
. It's a standard way to merge objects in modern JavaScript.firstObject
and secondObject
and assign them to a new object. It's a more verbose way to merge objects but provides some additional safety checks.Library and Special Features
There are no explicit libraries mentioned in the benchmark. However, some features like Object.assign()
rely on the ECMAScript standard, which is a set of standardized specifications for JavaScript.
The spread operator (...
) was introduced in ECMAScript 2015 (ES6) and has since become a widely supported feature in modern browsers and versions of JavaScript.
For-In Loop and Null Checks
The For-In loop with null checks is a common pattern used to iterate over object properties in older browsers or versions of JavaScript that don't support more modern approaches like Object.assign()
or the spread operator. The null check helps prevent errors when dealing with objects that may not have certain properties.
Other Alternatives
Some alternative approaches to merging objects without mutation include:
merge()
methods provided by libraries like Lodash or Ramda.reduce()
method on an array of key-value pairs.However, these alternatives might be overkill for simple use cases and may introduce additional dependencies or complexity.