how to use process.hrtime to get execution time of async function - node.js

Question

I am triing to get execution time of async function. Seemingly I can use process.hrtime for this. I created simple example:
console.log("starting");
var start = process.hrtime();
console.log("start");
console.log(start);
setTimeout(function(){
console.log("HELLO");
var end = process.hrtime();
console.log("end");
console.log(end);
}, 1000);
It outputs
starting
start
[ 131806, 731009597 ]
HELLO
end
[ 131807, 738212296 ]
But I don't understand where is exectuion time in miliseconds? I expect to get 1000 ms in this example.

Answer 1

Got it:
console.log("starting");
var start = process.hrtime();
console.log("start");
console.log(start);
setTimeout(function(){
console.log("HELLO");
var end = process.hrtime(start);
console.log("end");
console.log(end);
}, 1000);
Prints
starting
start
[ 132798, 207101051 ]
HELLO
end
[ 1, 7001730 ]
That means 1 second and 7001730 nanoseconds from start to end

Answer 2

Since Node 10.7.0, process.hrtime is marked as 'legacy', with the recommended method being process.hrtime.bigint. The documentation contains an example of how to use this method to time an operation:
const start = process.hrtime.bigint();
// 191051479007711n
setTimeout(() => {
const end = process.hrtime.bigint();
// 191052633396993n
console.log(`Benchmark took ${end - start} nanoseconds`);
// Benchmark took 1154389282 nanoseconds
}, 1000);

Answer 3

Just to add in case someone needs the execution time in ms:
console.log("starting");
var start = process.hrtime();
console.log("start");
console.log(start);
setTimeout(function(){
console.log("HELLO");
var end = process.hrtime(start); // end[0] is in seconds, end[1] is in nanoseconds
const timeInMs = (end[0]* 1000000000 + end[1]) / 1000000; // convert first to ns then to ms
console.log("timeInMs:", timeInMs);
}, 1000);

Answer 4

Here's a simple wrapper timing function for async functions:
// async function execution time wrapper
async function fnTime(fn, ...params) {
const start = process.hrtime()
const result = await fn(...params)
const end = process.hrtime(start)
console.log(
`[${fn.name}] Execution time:${(end[0] * 1000000000 + end[1]) /
1000000} ms`
)
return result
}
example usage (see this demo on repl.it):
// usage
const setTimeoutPromise = ms => new Promise(resolve => setTimeout(resolve, ms))
// example 2:
// get name from db
const db = {
async getUser(id){
// simulate wait for record retrival from db
await fnTime(setTimeoutPromise, 150)
return {
_id: id,
name: 'John Doe',
organisation: 'UN',
email: 'johndoe#un.org'
}
}
}
// test it
;(async function(){
const result = await fnTime(db.getUser, 'asfa98th4nfwef0qwrwef0')
console.log('result', result)
})()
// result:
// [setTimeoutPromise] Execution time:197.928094 ms
// [getUser] Execution time:199.480553 ms