Benchmark: for-in vs Object.key

Script Preparation code:

var objects = [];
for(var i =0;i<1000;i++){
  var object = {}; // dynamic create object, browser can't cache it
  object["p1"] = 1+i;
  object["p2"] = 2+i;
  object["p3"] = 3+i;
  object["p4"] = 4+i;
  object["p5"] = 5+i;
  object["p6"] = 6+i;
  object["p7"] = 7+i;
  object["p8"] = 8+i;
  object["p9"] = 9+i;
  objects.push(object);
}

function loop1(object){
    var keys = Object.keys(object);
    var r = 0;
    for(var i=0, len2 = keys.length;i<len2;i++){
        r += object[keys[i]];
    }
  
    return r;
}

function loop2(object){
    var keys = Object.getOwnPropertyNames(object);
    var r = 0;
    for(var i=0, len2 = keys.length;i<len2;i++){
        r += object[keys[i]];
    }
  
    return r;
}

function loop3(object){
  var r = 0;
  for(var k in object){
     r += object[k];
  }
  
  return r;
}

Tests:

Object.keys
for(var j=0,len=objects.length;j<len;j++){ loop1(objects[j]); }
Object.getOwnPropertyNames
for(var j=0,len=objects.length;j<len;j++){ loop2(objects[j]); }
for... in...
for(var j=0,len=objects.length;j<len;j++){ loop3(objects[j]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.keys
Object.getOwnPropertyNames
for... in...

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation.

The provided JSON represents a JavaScript benchmark test case on MeasureThat.net. The test measures the performance of three different ways to iterate over an object's properties: `Object.keys()`, `Object.getOwnPropertyNames()`, and the traditional `for... in...` loop.

**Option 1: Object.keys()**

This method returns an array of strings representing the property names of the object. It's a modern, non-intrusive way to get the property names without relying on proprietary browser features.

Pros:

* Non-intrusive, meaning it doesn't add any extra properties or methods to the original object.
* Fast and efficient, as it only returns a reference to the existing property name array.
* Works across different browsers and Node.js versions.

Cons:

* Requires modern JavaScript features (ES6+).
* May not work in older browsers that don't support this method.

**Option 2: Object.getOwnPropertyNames()**

This method returns an array of strings representing all properties (including non-enumerable ones) of the object. It's similar to `Object.keys()`, but it includes non-enumerable properties as well.

Pros:

* Works in older browsers that don't support `Object.keys()`.
* Includes non-enumerable properties, which may be important for certain use cases.
* Still relatively fast and efficient.

Cons:

* Adds an extra method call to the original object, making it slightly slower than `Object.keys()`.
* May not work in modern browsers that prefer or require `Object.keys()`.

**Option 3: for... in...**

This traditional loop iterates over the object's properties using its own syntax. It's often used when you need more control over the iteration process, but it can be slower and less efficient than other methods.

Pros:

* Works across all browsers and Node.js versions.
* Provides more control over the iteration process.
* Can be useful when working with non-standard objects or complex property names.

Cons:

* Slower and less efficient compared to `Object.keys()` and `Object.getOwnPropertyNames()`.
* May add unnecessary properties or methods to the original object, depending on how it's implemented.

In summary, the choice of method depends on your specific use case and requirements. If you're targeting modern browsers and want a fast, non-intrusive way to iterate over an object's properties, `Object.keys()` is likely the best choice. For older browsers or scenarios where non-enumerable properties are important, `Object.getOwnPropertyNames()` might be more suitable. The traditional `for... in...` loop is generally slower and less efficient but can still be useful in certain situations.

Other alternatives to consider:

* `Reflect.ownKeys()`: This method returns an array of strings representing the property names of the object, including non-enumerable ones. It's similar to `Object.getOwnPropertyNames()`, but more modern and efficient.
* Using a library or framework like Lodash or Ramda, which provide utilities for working with objects and arrays.

Note that this explanation focuses on JavaScript-specific aspects of the benchmark test case. Other considerations, such as caching, parallelization, or profiling optimizations, might be relevant depending on the specific use case.

Related benchmarks:

for-in vs Object.key (version: 7)

Comparing performance of: Object.keys vs Object.getOwnPropertyNames vs for... in...

Created: 9 years ago by: Registered User

Jump to the latest result

Object.keys

Object.getOwnPropertyNames

for... in...

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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