Is there a more accurate way to create a Javascript timer than setTimeout?

Question

Something that has always bugged me is how unpredictable the setTimeout() method in Javascript is.

In my experience, the timer is horribly inaccurate in

Answer 1

Here are what I use. Since it's JavaScript, I will post both my Frontend and node.js solutions:

For both, I use the same decimal rounding function that I highly recommend you keep at arms length because reasons:

const round = (places, number) => +(Math.round(number + `e+${places}`) + `e-${places}`)

places - Number of decimal places at which to round, this should be safe and should avoid any issues with floats (some numbers like 1.0000000000005~ can be problematic). I Spent time researching the best way to round decimals provided by high-resolution timers converted to milliseconds.

that + symbol - It is a unary operator that converts an operand into a number, virtually identical to Number()

Browser

const start = performance.now()

// I wonder how long this comment takes to parse

const end = performance.now()

const result = (end - start) + ' ms'

const adjusted = round(2, result) // see above rounding function

node.js

// Start timer
const startTimer = () => process.hrtime()

// End timer
const endTimer = (time) => {
    const diff = process.hrtime(time)
    const NS_PER_SEC = 1e9
    const result = (diff[0] * NS_PER_SEC + diff[1])
    const elapsed = Math.round((result * 0.0000010))
    return elapsed
}

// This end timer converts the number from nanoseconds into milliseconds;
// you can find the nanosecond version if you need some seriously high-resolution timers.

const start = startTimer()

// I wonder how long this comment takes to parse

const end = endTimer(start)

console.log(end + ' ms')