Benchmark: object.assign vs spread (when base object is large) fixed

Script Preparation code:

var baseObj = {"field0":"value0","field1":"value1","field2":"value2","field3":"value3","field4":"value4","field5":"value5","field6":"value6","field7":"value7","field8":"value8","field9":"value9","field10":"value10","field11":"value11","field12":"value12","field13":"value13","field14":"value14","field15":"value15","field16":"value16","field17":"value17","field18":"value18","field19":"value19","field20":"value20","field21":"value21","field22":"value22","field23":"value23","field24":"value24","field25":"value25","field26":"value26","field27":"value27","field28":"value28","field29":"value29","field30":"value30","field31":"value31","field32":"value32","field33":"value33","field34":"value34","field35":"value35","field36":"value36","field37":"value37","field38":"value38","field39":"value39","field40":"value40","field41":"value41","field42":"value42","field43":"value43","field44":"value44","field45":"value45","field46":"value46","field47":"value47","field48":"value48","field49":"value49","field50":"value50","field51":"value51","field52":"value52","field53":"value53","field54":"value54","field55":"value55","field56":"value56","field57":"value57","field58":"value58","field59":"value59","field60":"value60","field61":"value61","field62":"value62","field63":"value63","field64":"value64","field65":"value65","field66":"value66","field67":"value67","field68":"value68","field69":"value69","field70":"value70","field71":"value71","field72":"value72","field73":"value73","field74":"value74","field75":"value75","field76":"value76","field77":"value77","field78":"value78","field79":"value79","field80":"value80","field81":"value81","field82":"value82","field83":"value83","field84":"value84","field85":"value85","field86":"value86","field87":"value87","field88":"value88","field89":"value89","field90":"value90","field91":"value91","field92":"value92","field93":"value93","field94":"value94","field95":"value95","field96":"value96","field97":"value97","field98":"value98","field99":"value99"}
var newObj = {"n0":"v0","n1":"v0","n2":"v0","n3":"v0","n4":"v0"}

Tests:

object.assign
var c = Object.assign(baseObj, newObj);
spread
var c = {...baseObj, ...newObj}
without immutable
Object.keys(newObj).forEach(key=>(baseObj[key]=newObj[key]))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
object.assign
spread
without immutable

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):

LLMs can make mistakes. Check important info.

Measuring the performance of object assignments in JavaScript is an interesting benchmark.

**Benchmark Definition**

The benchmark tests three different ways to assign properties to an existing object (`baseObj`) using either the `Object.assign()` method, the spread operator (`...`), or manually iterating over the keys of the `newObj` object and assigning values to `baseObj`.

**Options being compared:**

1. **object.assign()**: This is a built-in JavaScript method that creates a new object with the properties of two or more source objects.
2. **Spread operator (`...`)**: This is a shorthand syntax for creating a new object with the properties of an existing object and one or more additional objects.
3. **Manual iteration without immutability**: This approach involves iterating over the keys of `newObj` and assigning values to `baseObj` using direct property access.

**Pros and Cons:**

*   **object.assign()**:
    *   Pros: Simple, readable syntax; well-documented; widely supported.
    *   Cons: Can be slower for large objects due to the overhead of method call and object creation.
*   **Spread operator (`...`)**:
    *   Pros: Efficient for creating new objects with similar properties; concise syntax.
    *   Cons: May not work as expected if `baseObj` is not an object (e.g., if it's a string or number); can be slower due to the overhead of object creation.
*   **Manual iteration without immutability**:
    *   Pros: Can be faster for large objects since no overhead is created; controlled iterations ensure data integrity.
    *   Cons: More verbose syntax; requires more effort to maintain.

**Library and special JS feature usage**

The `Object.keys()` method, which is used in the "without immutable" option, is a built-in JavaScript library that returns an array of a given object's own enumerable property names. This method does not require any external libraries or special JavaScript features.

**Other considerations**

*   The benchmark assumes that both `baseObj` and `newObj` are objects. If either of them can be other types (e.g., strings, numbers), the results may vary.
*   The benchmark runs on a desktop machine with Chrome 67 and Mac OS X 10.13.5.

**Alternative approaches**

Other alternatives to these three options include:

1.  **Lodash's `assignIn()` method**: This is another popular library for performing object assignments, which can provide more flexibility and control over the assignment process.
2.  **Immutable data structures**: Using immutable data structures (e.g., Immutable.js) instead of mutable objects can eliminate the need for manual iteration or explicit immutability checks.
3.  **Native Web Workers**: Running benchmarks in native Web Workers environments may help isolate performance variations due to different JavaScript engines and caching behaviors on different platforms.

When choosing an object assignment method, consider factors such as code readability, maintainability, performance requirements, and potential edge cases that might affect the chosen approach.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36

Browser/OS: Chrome 67 on Mac OS X 10.13.5

View result in a separate tab

Test name	Executions per second
object.assign	919586.4 Ops/sec
spread	34311.0 Ops/sec
without immutable	534429.4 Ops/sec

Related benchmarks:

object.assign vs spread (when base object is large) fixed (version: 0)

Comparing performance of: object.assign vs spread vs without immutable

Created: 6 years ago by: Guest

Jump to the latest result

object.assign

spread

without immutable

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):