Benchmark: new Date instantiation performance

HTML Preparation code:

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Script Preparation code:

/*your preparation JavaScript code goes here
To execute async code during the script preparation, wrap it as function globalMeasureThatScriptPrepareFunction, example:*/
async function globalMeasureThatScriptPrepareFunction() {
    // This function is optional, feel free to remove it.
    // await someThing();
}

Tests:

from string
/*When writing async/deferred tests, use `deferred.resolve()` to mark test as done*/ new Date("2025-07-10T00:45:42.861Z")
from 0
new Date(0)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
from string
from 0

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36 Edg/141.0.0.0

Browser/OS: Chrome 141 on Windows

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from 0

5.4M/s

from string

2.4M/s

View exact numbers

Test name	Executions per second
✓ from 0	5,434,811 Ops/sec
from string	2,372,375 Ops/sec

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

LLMs can make mistakes. Check important info.

In the provided JSON, the benchmark focuses on measuring the performance of different methods of instantiating JavaScript `Date` objects. Two specific test cases are compared:

1. **Test Case: from string**
   - **Benchmark Definition**: `new Date("2025-07-10T00:45:42.861Z")`
   - This test case creates a `Date` object from a string representation of a date, specifically an ISO 8601 format string.

2. **Test Case: from 0**
   - **Benchmark Definition**: `new Date(0)`
   - This test case creates a `Date` object from the numeric value `0`, which corresponds to January 1, 1970, 00:00:00 UTC.

### Comparisons and Considerations

#### Performance Observations
According to the benchmark results:
- **from 0**: 49,753,692 executions per second
- **from string**: 10,287,521 executions per second

Clearly, creating a `Date` from a numeric value is significantly faster than creating it from a string.

#### Pros and Cons of Different Approaches

- **From String (`new Date("...")`)**
  - **Pros**:
    - More flexible and human-readable; can create dates from various string formats.
    - Supports time zone specifications when using ISO strings.
  - **Cons**:
    - Performance overhead associated with parsing the string and converting it to a date object.
    
- **From 0 (`new Date(0)`)**
  - **Pros**:
    - Extremely fast as it directly maps a numeric timestamp to the corresponding date.
    - Predictable and unambiguous since it represents the epoch time (January 1, 1970).
  - **Cons**:
    - Not flexible; it can only instantiate a specific date (January 1, 1970) when passed `0`. Additional logic is required for creating dates other than this.

### Other Alternatives

Besides these two methods of creating Date objects, JavaScript offers other options:

1. **Using Timestamps (milliseconds)**
   - You can create dates using timestamps, where you can specify a number of milliseconds since January 1, 1970. For example: `new Date(1609459200000)` (which corresponds to January 1, 2021).
   - This allows for precise date creation more succinctly than a string for simple use cases.

2. **Using getDate() Methods**
   - If you have year, month, date, etc., you can also use `new Date(year, monthIndex, day)`, which could be a more readable way to create dates, though it requires more parameters.

3. **Using Libraries**
   - Libraries such as **Moment.js** or **date-fns** enhance date manipulation and formatting but usually at a cost of performance due to their additional functionalities.
   - These libraries provide a more powerful interface for date handling, including time zones, formatting, and arithmetic operations—but they also add overhead in terms of file size and complexity.

### Conclusion

In conclusion, the benchmark effectively illustrates the stark difference in performance when instantiating JavaScript Date objects with different methods. Understanding these trade-offs is essential for developers aiming for optimized date handling in their applications.

new Date instantiation performance (version: 1)

Comparing performance of: `from string vs from 0`

Created: one year ago by: Guest

Go to the latest result

from string

from 0

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

new Date instantiation performance (version: 1)

Comparing performance of: from string vs from 0

Created: one year ago by: Guest

Go to the latest result

from string

from 0

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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Comparing performance of: `from string vs from 0`