Benchmark: Delete vs set undefined

Script Preparation code:

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

Tests:

Delete
delete obj.a; delete obj.b; delete obj.c; delete obj.d;
Set undefined
obj.a = undefined; obj.b = undefined; obj.c = undefined; obj.d = undefined;

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 74 runs

Delete

32.2M/s

Set undefined

30.1M/s

View exact numbers

✓ Delete: 32,239,960 ops/sec
• Set undefined: 30,084,050 ops/sec

Firefox 20 runs

Set undefined

297.7M/s

Delete

19.1M/s

Fastest: Set undefined (15.6x faster)

View exact numbers

✓ Set undefined: 297,714,048 ops/sec
• Delete: 19,060,756 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

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: 3 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:78.0) Gecko/20100101 Firefox/78.0

Browser/OS: Firefox 78 on Mac OS X 10.11

View result in a separate tab

Set undefined

4.7M/s

Delete

1.7M/s

View exact numbers

Test name	Executions per second
✓ Set undefined	4,720,428 Ops/sec
Delete	1,714,054 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

The provided JSON represents two JavaScript microbenchmarks on MeasureThat.net, testing the performance of deleting properties from an object versus setting them to `undefined`. We'll break down each test case, explore the differences between these approaches, and discuss pros and cons.

**Test Cases**

There are two individual test cases:

1. **Delete**: This test case deletes the properties `a`, `b`, `c`, and `d` from an object using the `delete` keyword.
```javascript
delete obj.a;
delete obj.b;
delete obj.c;
delete obj.d;
```
2. **Set undefined**: This test case sets each property to `undefined` using the assignment operator (`=`).
```javascript
obj.a = undefined;
obj.b = undefined;
obj.c = undefined;
obj.d = undefined;
```

**Options Compared**

The two approaches have different performance characteristics:

*   **Delete**: When you use the `delete` keyword, JavaScript needs to traverse the object's prototype chain to find the property and then perform the deletion. This can be slower than directly setting a property to `undefined`.
*   **Set undefined**: Directly setting a property to `undefined` is faster because it doesn't involve traversing the prototype chain.

**Pros and Cons**

Here are some pros and cons of each approach:

*   **Delete**:
    *   Pros:
        +   Less memory usage, as the object is not modified.
        +   May be more suitable for certain use cases where you need to remove properties without modifying the original object.
    *   Cons:
        +   Slower performance due to the traversal of the prototype chain.
*   **Set undefined**:
    +   Pros:
        +   Faster performance since it doesn't involve traversing the prototype chain.
    +   Cons:
        -   More memory usage, as the original property values are stored in memory until they're garbage collected.

**Library and Special Features**

There is no explicit library mentioned in the provided JSON. However, note that modern JavaScript engines like V8 (used by Chrome) and SpiderMonkey (used by Firefox) provide various features to optimize object deletion performance, such as:

*   **WeakMap**: A data structure that stores keys and values using a WeakReference, which allows for garbage collection of keys.
*   **Object.getOwnPropertyNames()** and **Object.prototype.hasOwnProperty.call()**: These methods can be used to iterate over an object's properties, allowing for more efficient property deletion.

**Special JavaScript Features**

There are no special JavaScript features explicitly mentioned in the provided JSON. However, if you're interested in exploring other optimization techniques or performance-related topics, some notable features include:

*   **Array.prototype.forEach()**: Optimized for performance by using a sparse array to reduce memory allocation.
*   **Symbol properties**: Introduced in ECMAScript 2015 (ES6), which provide an efficient way to store and retrieve data without collision issues.

**Alternatives**

If you're interested in exploring alternative approaches or optimizing object deletion performance, consider the following alternatives:

*   Use a `WeakMap` instead of deleting individual properties.
*   Implement your own property deletion mechanism using `Object.prototype.hasOwnProperty.call()` and iteration over the object's properties.
*   Consider using other data structures like a `Set` to store unique keys.

Keep in mind that these alternatives might come with their own trade-offs in terms of performance, memory usage, or code complexity.

Delete vs set undefined (version: 1)

Comparing performance of: `Delete vs Set undefined`

Created: 9 years ago by: Registered User

Go to the latest result

Delete

Set undefined

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 74 runs

Firefox 20 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Delete vs set undefined (version: 1)

Comparing performance of: Delete vs Set undefined

Created: 9 years ago by: Registered User

Go to the latest result

Delete

Set undefined

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 74 runs

Firefox 20 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `Delete vs Set undefined`