Benchmark: Date.now() vs new Date().getTime() vs cast new Date()

Script Preparation code:

var timestamp = null;

Tests:

Date.now()
timestamp = Date.now();
new Date().getTime();
timestamp = new Date().getTime();
+new Date();
timestamp = +new Date();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Date.now()
new Date().getTime();
+new Date();

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of what is being tested on the provided JSON benchmark.

**Benchmark Overview**

The benchmark is comparing three different ways to get the current timestamp in JavaScript:

1. `Date.now()`
2. `new Date().getTime()`
3. `+new Date()` (using the unary plus operator)

**Options Compared**

The test cases are comparing the performance of each option, which means we're looking at how many times each operation can be executed per second.

* `Date.now()`: This method returns the number of milliseconds since the Unix Epoch (January 1, 1970, 00:00:00 UTC) as a fixed-point number. It's designed to provide high-resolution timing.
* `new Date().getTime()`: This method returns the number of milliseconds since the Unix Epoch for the specified date and time. However, due to its implementation, it can be slower than `Date.now()` because it takes into account the time zone and daylight saving time adjustments.
* `+new Date()`: This is a trick that uses the unary plus operator (`+`) to force JavaScript to perform a primitive conversion on the result of calling `new Date()`, effectively casting the result to a number. While this might seem like an optimization, it's actually just syntactic sugar for `Date.now()`.

**Pros and Cons**

* **`Date.now()`**: Pros: fast, accurate, and widely supported. Cons: assumes a fixed-point representation of time, which can lead to issues with very large or very small timestamps.
* **`new Date().getTime()`**: Pros: takes into account time zone and daylight saving time adjustments. Cons: slower than `Date.now()`, as it's more complex and involves more operations.
* **`+new Date()`**: Pros: syntactic sugar for `Date.now()`, so it might seem like an optimization. Cons: doesn't provide any actual performance benefits, and its documentation is less clear due to the syntax trickery.

**Library and Special JS Features**

There are no libraries used in this benchmark, but there's a special JavaScript feature being utilized:

* The unary plus operator (`+`) is used to force a primitive conversion on the result of calling `new Date()`. This is not a standard JavaScript feature, but rather an optimization technique.

**Other Considerations**

This benchmark is focused on measuring performance and comparing different approaches. However, it's essential to note that `Date.now()` should be preferred over `+new Date()` due to its simplicity and readability. The difference in performance between these two options is unlikely to have a significant impact on most use cases.

**Other Alternatives**

If you need more accurate timing or want to account for time zone adjustments, you might consider using other methods:

* For accurate timing: `performance.now()`, which returns the number of milliseconds since the page was loaded (or in older browsers, since the last navigation event).
* To account for daylight saving time changes: `Date.now()` with a specific time zone argument (e.g., `new Date().getTimezoneOffset()`) or using a library like moment.js.

In summary, this benchmark is testing different ways to get the current timestamp in JavaScript. While `+new Date()` might seem like an optimization, it's actually just syntactic sugar for `Date.now()`, and there are no significant performance differences between these options. The focus of this benchmark should be on highlighting the importance of using `Date.now()` for its simplicity, readability, and accurate timing.

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36

Browser/OS: Chrome 127 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Date.now()	7600728.0 Ops/sec
new Date().getTime();	7025969.5 Ops/sec
+new Date();	5529055.5 Ops/sec

Related benchmarks:

Date.now() vs new Date().getTime() vs cast new Date() (version: 0)

Comparing performance of: Date.now() vs new Date().getTime(); vs +new Date();

Created: 2 months ago by: Guest

Jump to the latest result

Date.now()

new Date().getTime();

+new Date();

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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