setTimeout syntax error ?

[brucemand]

this works;

	var msg="Thank you for visiting...\n\n BYE!";	alert(msg);

but this doesn't;

	var msg="Thank you for visiting...\n\n BYE!";	var t=setTimeout("alert(msg)",1500);

and THIS;

	var msg="Thank you for visiting...\n\n BYE!";	var t=setTimeout(alert(msg),1500);

results in this;

Error: useless setTimeout call (missing quotes around argument?)Source File: file:.../###/goodbye.htmLine: 19

what am i doing wrong ?EDIT: Error msg for the first failure;

Error: msg is not definedSource File: file:.../###/goodbye.htmLine: 19

[Synook]

The first setTimeout call doesn't work, because msg isn't in the right scope, and thus when the argument is evaluated msg is undefined. The second one doesn't work, because by calling alert() at that time you are actually trying to pass the return value of alert() (i.e. nothing) to setTimeout(). This would work:

var msg = "...";setTimeout(function() {	alert(msg);}, 1500);

[Ingolme]

I suggest never using a string as an argument for the setTimeout() and setInterval() methods.

[brucemand]

I suggest never using a string as an argument for the setTimeout() and setInterval() methods.

hmm, okay - then i suggest the w3schools page on said methods be changed accordingly.

[jeffman]

The w3schools examples tend to be extremely simplified to you can understand the focus of the tutorial at hand. The explains the unfortunate abundance of document.write statements. So I find myself sympathetic and frustrated at the same time.

[brucemand]

The w3schools examples tend to be extremely simplified to you can understand the focus of the tutorial at hand. The explains the unfortunate abundance of document.write statements. So I find myself sympathetic and frustrated at the same time.

yes, i suppose so.it's the starter kit, or Web Tech 101.i guess it's time i "graduated" to using MDN Docs more often.

[brucemand]

The first setTimeout call doesn't work, because msg isn't in the right scope, and thus when the argument is evaluated msg is undefined. The second one doesn't work, because by calling alert() at that time you are actually trying to pass the return value of alert() (i.e. nothing) to setTimeout(). This would work:

var msg = "...";setTimeout(function() {	alert(msg);}, 1500);

thanks, i see setTimeout() is just like any other function then.any idea why the tutorials use a var t=setTimeout() to initiate an instance ?'t' never seems to be referenced afterwards. :-/

[jeffman]

If you ever need to cancel the timeout target before it executes, you pass the variable to clearTimeout. So quite often the variable is global.

[thescientist]

thanks, i see setTimeout() is just like any other function then.any idea why the tutorials use a var t=setTimeout() to initiate an instance ?'t' never seems to be referenced afterwards. :-/

on the same page, in the example for clearInterval(), the t variable is used there to stop the timer.

[brucemand]

on the same page, in the example for clearInterval(), the t variable is used there to stop the timer.

ahh, okay - so unless it needs to be 'clear'-ed, var-ing it is unnecessary.