Question

Two questions:

1. How is the value returned from setInterval and setTimeout (the ones used to clear the timers) calculated?

2. Is it possible for both the functions to return the same value during runtime?
   For example:

   var a = setInterval(fn1, 1000);
var b = setTimeout(fn2, 1000);

Is it possible for a and b to have the same value?

The first one is more of a for-my-knowledge question, but the second one is more important.

Answer 1

Returns a value which can be used to cancel the timer. So, it would seem unlikely that they return the same value (unless they are reusing values and one of the timers has already been cancelled)

Mozilla states it’s DOM level 0, but not part of the specification. (look at the bottom of the page)

I’ve got an even better reference:

Nabble says:

SetTimeout and setInterval are from
the original Javascript specification,
pre-ECMA. That specification is not
officially standardized anywhere, but
it is supported by all web browsers
and most implementations of the
Javascript language. (Including
ActionScript.)

The pre-ECMA specs are often known as
the “DOM-0” APIs. Since they have
never been standardized before, it
makes sense for HTML5 to finally spec
the non-deprecated APIs in an attempt
to provide a consistent environment
across browsers. Especially when
recent events have proven that there
are companies who like to implement
the letter of the standard, but not
the spirit.

Read the original spec here, or from Sun (who was an early endorser of JavaScript).