The benchmark described tests the performance of two different methods for measuring time in JavaScript: Date.now() and performance.now(). Each of these methods has different characteristics that affect their precision and accuracy, making them suitable for different contexts in programming.
Options Compared
Date.now()
- Benchmark Definition:
timedif = Date.now() - Date.now();
- This method returns the number of milliseconds elapsed since January 1, 1970 (UTC). It is a straightforward way to obtain the current timestamp but lacks precision for measuring short time intervals.
performance.now()
- Benchmark Definition:
timedif = performance.now() - performance.now();
- This method returns a timestamp in milliseconds, accurate to one thousandth of a millisecond (microseconds). It is part of the Performance API and is designed specifically for high-resolution timing.
Pros and Cons
Date.now()
Pros:
- Simplicity: Easy to use and understand for basic timestamp retrieval.
- Broad compatibility: Supported in all modern browsers and older environments.
Cons:
- Lower precision: It provides time in whole milliseconds, making it less reliable for measuring short intervals accurately.
- Potential clock skew: The precision and accuracy can be affected by changes in system time or time zones.
performance.now()
Pros:
- High precision: Provides timestamps in microseconds, allowing more accurate measurements of short time intervals.
- Stable: It is less likely to be affected by changes to the system clock, as it works based on a performance timer that is typically high-resolution and monotonic (i.e., cannot go backwards).
Cons:
- Slightly more complex: Requires understanding of the Performance API, which might not be familiar to all developers.
- May not be available in very old environments or specific contexts (though it is widely supported in modern web browsers).
Other Considerations
- Usage Context: When selecting a method for timing, developers should consider the criticality of precision in their application. For general purposes or logging,
Date.now() might suffice. However, for performance-sensitive operations like animations, high-frequency data sampling, or micro-benchmarking, performance.now() is a better choice.
- Browser Compatibility: While both methods are supported in modern browsers, it's always a good practice to verify compatibility, especially if targeting older browsers or specific features.
Alternatives
Other alternatives for measuring time in JavaScript include:
- setTimeout/setInterval: While not direct timing functions, they can be used in conjunction with the above methods for delays and interval measurements.
- console.time() and console.timeEnd(): These provide a convenient way to measure elapsed time between two points in code without explicitly working with timestamps, leveraging
performance.now() under the hood in most environments.
- Custom High-Resolution Timers: For very specific scenarios, developers may implement custom timing setup using
requestAnimationFrame for synchronizing with browser rendering cycles.
In conclusion, this benchmark aims to provide clarity on the efficiency and effectiveness of two standard time measurement functions in JavaScript, informing developers about their appropriate usage in performance-critical applications.
