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

Script Preparation code:

var timestamp = null;

Tests:

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

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36

Browser/OS: Chrome 102 on Windows

View result in a separate tab

Test name	Executions per second
Date.now()	2663225.2 Ops/sec
new Date().getTime();	2053386.0 Ops/sec
+ new Date	2461302.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what is tested on the microbenchmark.

**Benchmark Definition**

The benchmark definition is a JSON object that contains three test cases:

1. `Date.now()`: This test case measures the performance of the `Date.now()` function, which returns the number of milliseconds since the Unix Epoch (January 1, 1970).
2. `new Date().getTime()`: This test case measures the performance of the `new Date()` constructor followed by the `getTime()` method, which also returns the number of milliseconds since the Unix Epoch.
3. `+ new Date`: This test case measures the performance of a bitwise shift operation (`+` operator) applied to a newly created `Date` object.

**Options Compared**

The three options are compared in terms of their execution time (in milliseconds per second).

**Pros and Cons of Each Approach**

1. **`Date.now()`**:
	* Pros: Simple, concise, and widely supported.
	* Cons: May not be as precise as other methods, especially for very large timestamps.
2. **`new Date().getTime()`**:
	* Pros: More precise than `Date.now()`, as it creates a new `Date` object and returns its timestamp.
	* Cons: More complex and may have performance overhead due to the creation of a new `Date` object.
3. **`+ new Date`**:
	* Pros: May be faster due to the bitwise shift operation, which is often optimized by the JavaScript engine.
	* Cons: Less intuitive and less widely supported than the other two options.

**Library/Function Used**

None of these test cases use any external libraries or functions. They only rely on built-in JavaScript features.

**Special JS Features/Syntax**

The test case `+ new Date` uses a bitwise shift operation, which is not explicitly documented in the standard. However, it is a common optimization technique used by some JavaScript engines to improve performance. The `-0` suffix is also used, which is an ES6 feature that allows for optional sign extension.

**Other Considerations**

When writing benchmarks like this one, consider the following:

* Use a consistent testing environment and platform.
* Warm up the test environment before running the benchmark (e.g., by executing some trivial code).
* Run multiple executions of each test case to get an accurate average execution time.
* Consider adding noise or variations to the input data to simulate real-world scenarios.

**Alternative Approaches**

If you need to compare the performance of different date-related functions in JavaScript, here are some alternative approaches:

1. Use `Date.now()` consistently across all test cases.
2. Use `new Date()` and `getTime()` together to create a new `Date` object and return its timestamp.
3. Compare the performance of different date parsing algorithms (e.g., using regular expressions).
4. Test the performance of different date formatting libraries or functions.

Keep in mind that these alternative approaches may have different trade-offs in terms of simplicity, precision, and overhead.

Related benchmarks:

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

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

Created: 2 years 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 2 months ago):