Benchmark: Delete vs set undefined for Object field

Script Preparation code:

var obj = {a:1, b:2, c:3, d:4};

Tests:

Delete
delete obj.c;
Set undefined
obj.c = undefined;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Delete
Set undefined

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:143.0) Gecko/20100101 Firefox/143.0

Browser/OS: Firefox 143 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Delete	63654488.0 Ops/sec
Set undefined	1058150592.0 Ops/sec

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

LLMs can make mistakes. Check important info.

In this benchmark, the performance of two different methods for modifying fields in a JavaScript object is being tested: using the `delete` operator and assigning a value of `undefined` to an object property.

### Options Compared
1. **Delete**: The first method, `delete obj.c;`, utilizes the `delete` operator. This operator removes a property from an object.
2. **Set undefined**: The second method, `obj.c = undefined;`, assigns the value `undefined` to the object property `c`, effectively indicating that the property exists but has no meaningful value.

### Pros and Cons
#### 1. Delete Operator
**Pros**:
- Removes the property completely from the object. This can result in a smaller object size when iterating or serializing the object.

**Cons**:
- The performance of the `delete` operator can be suboptimal in some JavaScript engines, especially if the object has been optimized for property access. Deleting properties may de-optimize an object in terms of performance, resulting in slower property access times for future operations due to the change in the internal representation of the object.

#### 2. Set Undefined
**Pros**:
- Generally faster than using `delete`, as it does not modify the object's structure—only the value of the property is changed. Most JavaScript engines maintain the optimized property access even after modifying the value.

**Cons**:
- The property still exists on the object; thus, the size of the object remains unchanged. If you check properties using methods like `Object.keys()`, this still returns the property as part of the object.

### Other Considerations
- **Memory Usage**: The `delete` operator may lead to reduced memory usage if many properties are deleted from large objects. Conversely, setting properties to `undefined` may lead to increased memory usage if many undefined properties are retained in objects.
- **Usage in Code**: The choice between these two often depends on the context within a codebase. If the property is no longer needed at all, `delete` is appropriate; if the value of an existing property simply needs resetting without losing the property itself, setting it to `undefined` is suitable.

### Alternatives
- **Using Non-Enumerable Properties**: Instead of deleting or setting properties to `undefined`, you can create private or non-enumerable properties using `Object.defineProperty()`, which allows you to manage visibility while preserving the object's structure.
- **Object Prototypes**: Leveraging object prototype methods can provide a more structured approach to managing properties without directly modifying object instances.
- **Weak Maps**: For object-style storage of properties that need to be removed efficiently with little concern for memory leaks, using `WeakMap` can be a smart alternative since it allows for side-effects (automatic garbage collection) when objects that hold keys are no longer referenced.

In summary, this benchmark tests the performance implications of two approaches to property management within JavaScript objects, providing insights necessary for making informed decisions in software development regarding performance and memory management.

Related benchmarks:

Delete vs set undefined for Object field (version: 1)

Comparing performance of: Delete vs Set undefined

Created: one year ago by: Guest

Jump to the latest result

Delete

Set undefined

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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