Benchmark: hasOwnProperty vs Object.keys (longer and more options)

Script Preparation code:

var props = {a:1,b:1,c:1,d:1,e:1,f:1,g:1,h:1,i:1,j:1,k:1,l:1,m:1,n:1,o:1,p:1,q:1,r:1,s:1,t:1,u:1,v:1,w:1,x:1,y:1,z:1};
for (var i=0;i<1000;i++){
  var key = i.toString();
  props[i]=i;
}

Tests:

hasOwnProperty
for (const p in props) { if (Object.prototype.hasOwnProperty.call(props, p)) { props[p] = 2; } }
for (var k=Object.keys(props), [...]
for (var k=Object.keys(props), l=k.length, i=0; i<l; i++) { props[k[i]] = 2; }
for (var k_i=0;k_i<keys_l;k_i++
const keys = Object.keys(props); const keys_l = keys.length; for (var k_i=0;k_i<keys_l;k_i++){ const k=keys[k_i] props[k] = 2 }
for (const key in Object.keys(props))
for (const key in Object.keys(props)){ props[key] = 2 }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
hasOwnProperty
for (var k=Object.keys(props), [...]
for (var k_i=0;k_i<keys_l;k_i++
for (const key in Object.keys(props))

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36 Edg/134.0.0.0

Browser/OS: Chrome 134 on Windows

View result in a separate tab

Test name	Executions per second
hasOwnProperty	43399.1 Ops/sec
for (var k=Object.keys(props), [...]	99700.2 Ops/sec
for (var k_i=0;k_i<keys_l;k_i++	100077.6 Ops/sec
for (const key in Object.keys(props))	293.4 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

The provided benchmark compares different methods of iterating over object properties in JavaScript, specifically focusing on two main approaches: using `hasOwnProperty` and `Object.keys`. This evaluation is important in understanding how different styles of property access can impact performance in various scenarios.

### Options Compared

1. **Using `hasOwnProperty` with a `for...in` Loop**:
   ```javascript
   for (const p in props) {
     if (Object.prototype.hasOwnProperty.call(props, p)) {
       props[p] = 2;
     }
   }
   ```
   - **Test Name**: `hasOwnProperty`
   - **Description**: This method iterates over all enumerable properties of an object using the `for...in` statement and checks if each property is a direct property of the object using `hasOwnProperty`. 
   - **Pros**: It can identify properties directly on the object and ignore inherited properties.
   - **Cons**: The `for...in` loop iterates over all properties that are enumerable, leading to additional overhead due to the need for the `hasOwnProperty` check.

2. **Using `Object.keys` with a Loop**:
   ```javascript
   for (var k = Object.keys(props), l = k.length, i = 0; i < l; i++) {
     props[k[i]] = 2;
   }
   ```
   - **Test Name**: `for (var k=Object.keys(props), [...]`
   - **Description**: This method utilizes `Object.keys` to get an array of the object's own property names. It then iterates through that array to access each property.
   - **Pros**: This method only accesses the object's own properties directly and avoids the overhead of a check on each iteration.
   - **Cons**: It creates an array of keys which could lead to memory overhead when dealing with large objects.

3. **Using `Object.keys` with a For Loop Based on Length**:
   ```javascript
   const keys = Object.keys(props);
   const keys_l = keys.length;
   for (var k_i = 0; k_i < keys_l; k_i++) {
     const k = keys[k_i];
     props[k] = 2;
   }
   ```
   - **Test Name**: `for (var k_i=0;k_i<keys_l;k_i++`
   - **Description**: This approach is similar to the previous one but explicitly caches the length of the keys array to optimize the loop's condition check.
   - **Pros**: The pre-computed length can slightly enhance performance by avoiding repeated calculations.
   - **Cons**: Similar to the previous `Object.keys` method, this also has the memory overhead of creating an array of keys.

4. **Incorrect Syntax Usage of Object.keys in For...in Loop**:
   ```javascript
   for (const key in Object.keys(props)) {
     props[key] = 2;
   }
   ```
   - **Test Name**: `for (const key in Object.keys(props))`
   - **Description**: This approach misuses the `for...in` loop by iterating over the numeric indexes of the array returned by `Object.keys`, rather than the keys themselves.
   - **Pros**: None, as this does not achieve the intended goal properly.
   - **Cons**: This leads to incorrect access of properties, as it does not iterate over actual property names from the object.

### Performance Results

The benchmark's performance results reveal significant differences in execution speed:

- The **third method** (using `Object.keys` with a length caching optimization) showed the best performance at approximately **100K executions per second**.
- The **second method** (using `Object.keys` without length caching) is also efficient but slightly slower at around **99.7K executions per second**.
- Using **`hasOwnProperty` with a `for...in` loop** showed noticeably lower performance (around **43.3K executions per second**).
- The **fourth method** is not useful as it does not perform correctly and has an extremely low execution rate (~293 executions per second).

### Conclusion and Alternatives

This benchmark illustrates how different patterns for iterating over properties can affect execution speed. Using `Object.keys` methods is generally more efficient than using a `for...in` loop with `hasOwnProperty`, especially when accessing a large number of properties.

**Alternatives**:
- **Using `Map`** in cases where you require key-value pairs with guaranteed order and better performance for large datasets.
- **Using `forEach`** on the result of `Object.keys(props)` for better readability, although it might have performance overhead due to function calls.
- **Using modern `for...of`** loops with `Object.entries()` for cleaner syntax when you also need the values of the object properties, although it typically involves a similar overhead as `Object.keys`.

This benchmark serves to inform decisions based on performance considerations regarding object property iteration in JavaScript, facilitating choices between clarity and speed depending on the context.

Related benchmarks:

hasOwnProperty vs Object.keys (longer and more options) (version: 1)

Comparing performance of: hasOwnProperty vs for (var k=Object.keys(props), [...] vs for (var k_i=0;k_i<keys_l;k_i++ vs for (const key in Object.keys(props))

Created: one month ago by: Guest

Jump to the latest result

hasOwnProperty

for (var k=Object.keys(props), [...]

for (var k_i=0;k_i<keys_l;k_i++

for (const key in Object.keys(props))

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):