How do I measure the execution time of JavaScript code with callbacks?

Question

I have a piece of JavaScript code that I am executing using the node.js interpreter.

for(var i = 1; i <         


        

Answer 1

Surprised no one had mentioned yet the new built in libraries:

Available in Node >= 8.5, and should be in Modern Browers

https://developer.mozilla.org/en-US/docs/Web/API/Performance

https://nodejs.org/docs/latest-v8.x/api/perf_hooks.html#

Node 8.5 ~ 9.x (Firefox, Chrome)

// const { performance } = require('perf_hooks'); // enable for node
const delay = time => new Promise(res=>setTimeout(res,time))
async function doSomeLongRunningProcess(){
  await delay(1000);
}
performance.mark('A');
(async ()=>{
  await doSomeLongRunningProcess();
  performance.mark('B');
  performance.measure('A to B', 'A', 'B');
  const measure = performance.getEntriesByName('A to B')[0];
  // firefox appears to only show second precision.
  console.log(measure.duration);
  // apparently you should clean up...
  performance.clearMarks();
  performance.clearMeasures();         
  // Prints the number of milliseconds between Mark 'A' and Mark 'B'
})();

https://repl.it/@CodyGeisler/NodeJsPerformanceHooks

Node 12.x

https://nodejs.org/docs/latest-v12.x/api/perf_hooks.html

const { PerformanceObserver, performance } = require('perf_hooks');
const delay = time => new Promise(res => setTimeout(res, time))
async function doSomeLongRunningProcess() {
    await delay(1000);
}
const obs = new PerformanceObserver((items) => {
    console.log('PerformanceObserver A to B',items.getEntries()[0].duration);
      // apparently you should clean up...
      performance.clearMarks();
      // performance.clearMeasures(); // Not a function in Node.js 12
});
obs.observe({ entryTypes: ['measure'] });

performance.mark('A');

(async function main(){
    try{
        await performance.timerify(doSomeLongRunningProcess)();
        performance.mark('B');
        performance.measure('A to B', 'A', 'B');
    }catch(e){
        console.log('main() error',e);
    }
})();