Functions

function name(p1,p2, ...) {
}
               

function fibonacci(N) {
   var S = [];
   for (var i=0; i<N; i++) {
      if (i<2) {
         S.push(i);
      } else {
         S.push(S[i-1]+S[i-2]);
      }
   }
   return S;
}
               

What is the difference between fibonacci and fibonacci() ?

Timers

A timer schedules a function to execute in the future or on an interval.

A timeout:

function logSomething() {
   console.log("Hello future!");
}
var timer = setTimeout(logSomething,1000); // one second delay

On on an interval:

function logSomething() {
   console.log("Beuller?");
}
var interval = setInterval(logSomething,1000); // once every second

Or cancel them:

clearTimeout(timer);
clearInterval(interval);

For more information, see MDN setTimeout().

Why timers?

Don't camp on the main thread!

Imagine you respond to a mouse event and then do a bunch of work. What happens? Everything stops.

Instead:

• Inspect the event,
• do something immediately,
• or schedule something to happen in the future,
• then return.

Events

Some common events:

For more information, see MDN Event reference

Registering Event Listeners

Registration is by name on the scope: target.addEventListener(type,listener,useCapture)

function ouch() {
   alert("Ouch!");
}
var div = document.getElementById("#somebit");
div.addEventListener("click",ouch,false);
         

and you can remove it:

div.removeEventListener("click",ouch,false);
         

What is the purpose of useCapture ?

For more information, see MDN EventTarget.addEventListener

What is a callback?

1. A timer?
2. An interval?
3. An event listener?
4. All of the above?