How Can I Measure a JavaScript Function's Execution Time in Milliseconds?

Measuring Function Execution Time in Milliseconds

To determine the execution time of a function in milliseconds, several effective methods are available.

Performance.now()

The performance.now() function provides a timestamp representing the number of milliseconds elapsed since a specific point in time. To measure the execution time of a function using performance.now():

• Capture the starting timestamp: var startTime = performance.now().
• Execute the function you want to measure: doSomething().
• Capture the ending timestamp: var endTime = performance.now().
• Calculate the execution time: console.log(Call to doSomething took ${endTime - startTime} milliseconds`)`.

Note: In Node.js, you need to import the perf_hooks module:

const { performance } = require('perf_hooks');

Console.time()

A more straightforward approach is console.time(). It logs the start time of a measurement and automatically ends it later on. Inside the function you want to measure, use:

• Start the timer: console.time('doSomething').
• Execute the function: doSomething().
• End the timer: console.timeEnd('doSomething').

The time taken will be displayed in the console. Remember to have the same string passed to both time() and timeEnd() for the timer to work correctly.

Additional Notes:

• The precision of these methods can vary depending on the device and browser used.
• Use these methods cautiously when measuring code that runs for a very short duration, as the resolution may not be sufficient to capture small time intervals.

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