How good/bad is to call a function every second in a website ?

Question

Hello everybody. I am taking the JavaScript course and I found the following code to print out the current date.

function printTime() {
var d = new Date();
var hours = d.getHours();
var mins = d.getMinutes();
var secs = d.getSeconds();
document.body.innerHTML = hours+":"+mins+":"+secs;
}
setInterval(printTime, 1000);

As far as I know is good practice to add your scripts at the end of the body in html. This allows the website to load before the script runs. However I was wondering if calling a function will decrease the performance of the website once it is loaded.

Here the function is simple, but what if the function do something else more complex?

Answer 1

Not to worry, for machine, 1 second interval is considered a very long long period.

a CPU with a clock speed of 2 GHz can carry out two thousand million (2 000 000 000) cycles per second.

Answer 2

So there won't be a problem if a function is called every mili second because it will run on the local client CPU ? What about complexity. Does that affects ? I mean let's say that every mili seconds calculate some complex maths.