setInterval/setTimeout return value

javascript settimeout setinterval
aditya picture aditya · Jun 2, 2009 · Viewed 56.6k times · Source

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

cgp picture cgp · Jun 2, 2009

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).

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