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.

function greeting(name) {
  alert('Hello ' + name);
}

function processUserInput(callback) {
  var name = prompt('Please enter your name.');
  callback(name);
}

processUserInput(greeting);

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

Question 5

What do setTimeout() and setInterval() return?

Answer 5

intervalID is a numeric, non-zero value which identifies the timer created by the call to setInterval(); this value can be passed to clearInterval() to cancel the interval.