How Can I Efficiently Measure JavaScript Function Execution Time?

How to Measure Function Execution Duration

Measuring the execution time of a function can provide valuable insights into performance optimizations. There are several approaches to achieve this measurement.

Using performance.now() for Real-Time Performance Measurement

The modern approach for timing function execution is to utilize the performance.now() API. It returns the time elapsed since the start of the navigation in high-resolution milliseconds. To use it effectively:

1. Define a start time variable: var startTime = performance.now()
2. Execute the function whose duration you want to measure
3. Define an end time variable: var endTime = performance.now()
4. Calculate the execution time: console.log(Call to doSomething took ${endTime - startTime} milliseconds)

In Node.js, it's necessary to import the performance class using const { performance } = require('perf_hooks');.

Using console.time for Simple Time Measurement

The console.time method offers a straightforward way to measure execution time. However, it supports only one measurement at a time:

1. Start the timer: console.time('doSomething')
2. Execute the measured function: doSomething()
3. End the timer: console.timeEnd('doSomething')

The string passed to time() and timeEnd() must match to properly stop the timer. Refer to the MDN or Node.js documentation for detailed explanations.

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