How to measure execution time in JavaScript
Łukasz Holeczek
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Measuring execution time is essential for optimizing code and identifying performance bottlenecks in your JavaScript applications.
As the creator of CoreUI with over 25 years of development experience, I’ve measured and optimized thousands of functions across various projects.
The most straightforward and accurate solution is to use console.time() for quick measurements or performance.now() for high-precision timing.
Both methods are built into modern browsers and provide reliable results.
Use console.time() and console.timeEnd() to measure execution time quickly.
console.time('myOperation')
// Code to measure
let sum = 0
for (let i = 0; i < 1000000; i++) {
sum += i
}
console.timeEnd('myOperation')
The console.time() method starts a timer with a given label, and console.timeEnd() stops the timer and logs the elapsed time in milliseconds. For more precise measurements, you can use performance.now() which returns a high-resolution timestamp. This method is particularly useful when you need to calculate durations programmatically rather than just logging them to the console.
Best Practice Note
This is the same timing approach we use in CoreUI to benchmark component rendering and interaction performance. For production code, avoid leaving timing calls in place as they add overhead. Use performance.now() when you need microsecond precision or when building performance monitoring tools for real-world usage analytics.
