Is there any way to call a function periodically in JavaScript?

The setInterval() method, repeatedly calls a function or executes a code snippet, with a fixed time delay between each call. It returns an interval ID which uniquely identifies the interval, so you can remove it later by calling clearInterval().

var intervalId = setInterval(function() {
  alert("Interval reached every 5s")
}, 5000);

// You can clear a periodic function by uncommenting:
// clearInterval(intervalId);

See more @ setInterval() @ MDN Web Docs

Everyone has a setTimeout/setInterval solution already. I think that it is important to note that you can pass functions to setInterval, not just strings. Its actually probably a little "safer" to pass real functions instead of strings that will be "evaled" to those functions.

// example 1
function test() {
  alert('called');
}
var interval = setInterval(test, 10000);

Or:

// example 2
var counter = 0;
var interval = setInterval(function() { alert("#"+counter++); }, 5000);

Please note that setInterval() is often not the best solution for periodic execution - It really depends on what javascript you're actually calling periodically.

eg. If you use setInterval() with a period of 1000ms and in the periodic function you make an ajax call that occasionally takes 2 seconds to return you will be making another ajax call before the first response gets back. This is usually undesirable.

Many libraries have periodic methods that protect against the pitfalls of using setInterval naively such as the Prototype example given by Nelson.

To achieve more robust periodic execution with a function that has a jQuery ajax call in it, consider something like this:

function myPeriodicMethod() {
  $.ajax({
    url: ..., 
    success: function(data) {
      ...
    },
    complete: function() {
      // schedule the next request *only* when the current one is complete:
      setTimeout(myPeriodicMethod, 1000);
    }
  });
}

// schedule the first invocation:
setTimeout(myPeriodicMethod, 1000);

Another approach is to use setTimeout but track elapsed time in a variable and then set the timeout delay on each invocation dynamically to execute a function as close to the desired interval as possible but never faster than you can get responses back.