Benchmark: for-in to hasOwnProperty vs Object.keys, then loop

Script Preparation code:

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  var i;
  var key;
  var keys;
  var l;
  var value;

Tests:

for-in, then hasOwnProperty
for ( key in obj ) { if (obj.hasOwnProperty(key ) ) { value = obj[key]; } }
Object.keys, then loop
keys = Object.keys( obj ); i = keys.length; while( i--) { value = obj[ keys[ i ] ]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in, then hasOwnProperty
Object.keys, then loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Browser/OS: Firefox 63 on Windows 8.1

View result in a separate tab

Test name	Executions per second
for-in, then hasOwnProperty	11147.4 Ops/sec
Object.keys, then loop	7724.3 Ops/sec

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

LLMs can make mistakes. Check important info.

To answer your question, I'll need to infer that you're asking about the performance difference between using `for...in` loops with `hasOwnProperty()` versus `Object.keys()` and looping through the resulting array.

Based on the provided benchmark results, here are some observations:

1. **For-in loop with hasOwnProperty()**: The test with this approach has a higher execution rate (11147.353515625 exec/sec) compared to the test using `Object.keys()` and looping (7724.25927734375 exec/sec). This suggests that for-in loops with `hasOwnProperty()` might be faster, but with a slightly higher overhead due to the need to check if each property exists in the object.
2. **Object.keys() + loop**: The opposite is true for this approach: it's slower (7724.25927734375 exec/sec) compared to the for-in loop with `hasOwnProperty()`.

However, it's essential to note that these results are specific to Firefox 63 and might not generalize across browsers or edge cases.

**Recommendation**:

If performance is a top concern, using `Object.keys()` and looping through the resulting array might be a better choice. This approach provides more control over the iteration process and avoids the overhead of checking each property with `hasOwnProperty()`.

That said, if readability and simplicity are your priorities, a for-in loop with `hasOwnProperty()` can still be an excellent option, especially when dealing with objects that have a large number of properties.

Related benchmarks:

for-in to hasOwnProperty vs Object.keys, then loop (version: 0)

Comparing performance of: for-in, then hasOwnProperty vs Object.keys, then loop

Created: 6 years ago by: Guest

Jump to the latest result

for-in, then hasOwnProperty

Object.keys, then loop

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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