Settimeout Ignores Timeout? (Fires Immediately)

setTimeout ignores timeout? (Fires immediately)

You need to get rid of the parentheses on doFade().

The parentheses invoke the function instantly.

Just use this in stead: doFade

Why is the method executed immediately when I use setTimeout?

You're calling the function immediately and scheduling its return value.

Use:

setTimeout(testFunction, 2000);
                       ^

Notice: no parens.

Why does setTimeout() break for large millisecond delay values?

This is due to setTimeout using a 32 bit int to store the delay so the max value allowed would be

2147483647

if you try

2147483648

you get your problem occurring.

I can only presume this is causing some form of internal exception in the JS Engine and causing the function to fire immediately rather than not at all.

setTimeout -- callback executed immediately?

Several problems.

This invokes hide_info right away. Parenthesis invoke a function-object! (or are used for applying precedence to expressions).

That is,

this.id = setTimeout(this.hide_info(), 7000);

Is [mostly] equivalent to:

var temp = this.hide_info()       // call function ... uh, what?
this.id = setTimeout(temp, 7000)  // temp is "return" value ("undefined" here)

Oops! That's not right :) So take away the parenthesis. This will pass the function-object itself to the setTimeout. (Yes, functions are just objects in JavaScript. The expression this.hide_info is first evaluated to a function-object and, if there is a (...) after, it will invoke said function-object.)

this.id = setTimeout(this.hide_info, 7000)

However, it is still not correct because this inside the timeout function (hide_info) will be wrong! But this can be fixed with using a closure. (There are many great SO answers on the topic, feel free to search!)

var self = this
this.id = setTimeout(function () {
    // now in hide_info "this" will be "self", which was "this" ... outside :)
    self.hide_info()
}, 7000) 

(Or use Function.bind from ECMAScript ed5 or a library.)

Additionally, this.id is not the same as this.timeoutID, and is suspect for "correctness".

Keep it simple. It's okay to pass undefined/0 to clearTimeout: it'll silently ignore you.

cancel : function () {
    clearTimeout(this.id)  // but id is a horrid overloaded name :)
    this.id = undefined
}

Happy coding.

JavaScript setTimeout() won't wait to Execute?

alertBox()

Doesn't this look like an immediate function call?

Try passing the function (without executing it) instead:

setInterval(alertBox, 5000);

How can I make a part of code wait without halting everything else in JavaScript?

The issue you have is that you are not properly using the setTimeout function. You need to remove the parentheses from your call.

setTimeout(test, 3000);

Downvoters; I will make a more thorough and detailed answer for future readers later today when I’m at a computer. I am currently on break and do not have my computer with me. You can view some of my other answers to set your mind at ease that I will be back to flesh out a more detailed answer.

Why is setTimeout(fn, 0) sometimes useful?

In the question, there existed a race condition between:

1. The browser's attempt to initialize the drop-down list, ready to have its selected index updated, and
2. Your code to set the selected index

Your code was consistently winning this race and attempting to set drop-down selection before the browser was ready, meaning that the bug would appear.

This race existed because JavaScript has a single thread of execution that is shared with page rendering. In effect, running JavaScript blocks the updating of the DOM.

Your workaround was:

setTimeout(callback, 0)

Invoking setTimeout with a callback, and zero as the second argument will schedule the callback to be run asynchronously, after the shortest possible delay - which will be around 10ms when the tab has focus and the JavaScript thread of execution is not busy.

The OP's solution, therefore was to delay by about 10ms, the setting of the selected index. This gave the browser an opportunity to initialize the DOM, fixing the bug.

Every version of Internet Explorer exhibited quirky behaviors and this kind of workaround was necessary at times. Alternatively it might have been a genuine bug in the OP's codebase.

---

See Philip Roberts talk "What the heck is the event loop?" for more thorough explanation.

---

Related Topics