setTimeout — callback executed immediately? [duplicate]

Answer 1

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.