How Can I Accurately Measure Function Execution Time in JavaScript?

Accurately Measuring Function Execution Time

Measuring the time taken by a function to execute is a crucial aspect of performance optimization. This question explores various methods to achieve accurate measurements, showcasing the evolution of performance APIs over time.

Using performance.now()

Modern browsers and Node.js provide the performance.now() API, which is now the standard for measuring execution time. This API returns a high-resolution timestamp representing the elapsed time since an arbitrary point in the past.

var startTime = performance.now();

doSomething(); // Measured code

var endTime = performance.now();

console.log(`Call to doSomething took ${endTime - startTime} milliseconds`);

Using console.time()

For measuring execution time in a more user-friendly manner, the console.time() and console.timeEnd() methods can be used. These methods automatically output the elapsed time to the console.

console.time('doSomething');

doSomething(); // Measured function

console.timeEnd('doSomething');

It's important to note that the string passed to console.time() and console.timeEnd() must match to stop the timer correctly.

Evolution of Performance APIs

Over the years, the preferred method for measuring execution time has evolved:

• 2008: Using new Date().getTime(), which was limited by millisecond precision.
• Present: Using performance.now() and console.time(), which provide high-resolution timing.

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