JavaScript - What is setTimeout and setInterval?

setTimeout is used to execute some code after a specified amount of time. The function defined in setTimeout is queued in event loop after the specified interval. The execution would happen after the timeout, but might not execute immediately after timeout.

setTimeout(() => {
 console.log('Executes after timeout');
}, 1000);
//above code executes after 1000ms

setTimeout with 0ms timeout.

//Making timeout 0 does not make it synchronous
setTimeout(() => {
 console.log('Executes after 0 ms');
}, 0);
console.log('Execute on main thread.');
//above prints
//Execute on main thread.
//Executes after 0 ms

setInterval is used to execute some code repeatedly at an interval.

setInterval(function(){
  console.log('I am printed at an interval of 1 sec.');
}, 1000);