JavaScript-timers

Question 1

What is a “callback” function?

Answer 1

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.

Question 2

Besides adding an event listener callback function to an element or the document, what is one way to delay the execution of a JavaScript function until some point in the future?

Answer 2

setTimeout()

Question 3

How can you set up a function to be called repeatedly without using a loop?

Answer 3

setInterval()

Question 4

What is the default time delay if you omit the delay parameter from setTimeout() or setInterval()?

Answer 4

0 or act immediately

Question 5

What do setTimeout() and setInterval() return?

Answer 5

The returned timeoutID is a positive integer value which identifies the timer created by the call to setTimeout(). This value can be passed to clearTimeout() to cancel the timeout. It is guaranteed that a timeoutID value will never be reused by a subsequent call to setTimeout() or setInterval() on the same object (a window or a worker.) However, different objects use separate pools of IDs.