difference between return true; and return false;

#1 July 20th, 2005, 08:52 AM

Why does this work the way it does?
If someone could explain return true, and return false to me I'd
greatly appreciate it.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<html>
<head>
<title>Form.html</title>
</head>

<body>
<script language="JavaScript">
function form1_onsubmit() {
var returnValue = false;
if (document.form1.txtName.value == "") {
alert("Please Enter your Name");
document.form1.txtName.focus();
}
else {
returnValue = true;
}
return returnValue;
}
</script>

<form action="formhandler.asp" method="post" name="form1" onSubmit="
return form1_onsubmit()">
name: <input type="text" name="txtName">
<input type="submit" value="Go">

</form>

</body>
</html>

w i l l

#2 July 20th, 2005, 08:52 AM

"w i l l" <willis_31_40@yahoo.com> wrote in message
news:93hbgvg9o7sdlssthh7qtrq8gp23rk2uft@4ax.com...[color=blue]
> Why does this work the way it does?
> If someone could explain return true, and return false to me I'd
> greatly appreciate it.[/color]

When you return something from a function, that value gets returned to the
caller. For instance, say I had a method to multiply two numbers. Maybe the
code looks like this:

function multiply(num1, num2) {
return num1 * num2;
}
result = multiply(2, 4);

The function multiply will return the result of it's multiplication to
wherever it was called. The right-hand side of the result assignment is
where the function is called, so that is where the result is returned to.
So, in this case (with the parameters 2 and 4), it is the same as writing
result = 8;

When you are using return true or false with markup, you are indicating
whether or not you want the default action to happen after the javascript
has been executed. An example is needed:

<a href="somepage.html" onClick="alert('Hi'); return true;">Click Me</a>

When the link is clicked the javascript code for the onClick will run first,
and we get an alert. We have used return true, so that is saying when we
click OK to remove the alert, we do want to run the markup. So in this case
once we click OK to dismiss the alert, we would then be taken to
somepage.html. If we changed that to return false we would get the alert,
but wouldn't go to somepage.html.

So in your example if the method (form1_onsubmit) returns false, the default
behaviour of the form (action=formhandler.asp) won't run. In other words we
get the alert (thrown from inside the method), and when we click ok nothing
happens. If that method returns true though, the default behaviour will
occur, so the form will be submitted to the asp file.

Gareth

#3 July 20th, 2005, 08:52 AM

"w i l l" <willis_31_40@yahoo.com> wrote in message
news:93hbgvg9o7sdlssthh7qtrq8gp23rk2uft@4ax.com...[color=blue]
> Why does this work the way it does?
> If someone could explain return true, and return false to me I'd
> greatly appreciate it.[/color]

In a onxxxxx method where there is usually some form of standard processing
by the browser, it's just a way of specifying whether further standard
processing should take place.

Returning false means no, returning true means yes. So that example aborted
the submit if the user hasn't entered their name.

Nige

#4 July 20th, 2005, 08:52 AM

On Sat, 5 Jul 2003 04:49:02 +1000, "Gareth Church"
<gechurch@bigpond.com.au> wrote:
[color=blue]
>"w i l l" <willis_31_40@yahoo.com> wrote in message
>news:93hbgvg9o7sdlssthh7qtrq8gp23rk2uft@4ax.com.. .[color=green]
>> Why does this work the way it does?
>> If someone could explain return true, and return false to me I'd
>> greatly appreciate it.[/color]
>
>When you return something from a function, that value gets returned to the
>caller. For instance, say I had a method to multiply two numbers. Maybe the
>code looks like this:
>
>function multiply(num1, num2) {
> return num1 * num2;
>}
>result = multiply(2, 4);
>
>The function multiply will return the result of it's multiplication to
>wherever it was called. The right-hand side of the result assignment is
>where the function is called, so that is where the result is returned to.
>So, in this case (with the parameters 2 and 4), it is the same as writing
>result = 8;
>
>When you are using return true or false with markup, you are indicating
>whether or not you want the default action to happen after the javascript
>has been executed. An example is needed:
>
><a href="somepage.html" onClick="alert('Hi'); return true;">Click Me</a>
>
>When the link is clicked the javascript code for the onClick will run first,
>and we get an alert. We have used return true, so that is saying when we
>click OK to remove the alert, we do want to run the markup. So in this case
>once we click OK to dismiss the alert, we would then be taken to
>somepage.html. If we changed that to return false we would get the alert,
>but wouldn't go to somepage.html.
>
>So in your example if the method (form1_onsubmit) returns false, the default
>behaviour of the form (action=formhandler.asp) won't run. In other words we
>get the alert (thrown from inside the method), and when we click ok nothing
>happens. If that method returns true though, the default behaviour will
>occur, so the form will be submitted to the asp file.
>
>Gareth
>[/color]

Excellent explination, Thanks!

#5 July 20th, 2005, 08:52 AM

In article <93hbgvg9o7sdlssthh7qtrq8gp23rk2uft@4ax.com>, willis_31_40
@yahoo.com says...[color=blue]
> Why does this work the way it does?
> If someone could explain return true, and return false to me I'd
> greatly appreciate it.
>[/color]

It's a boolean thing - you wouldnt understand.

Just kidding :)

--

Remove NOT from email address to reply. AntiSpam in action.

#6 July 20th, 2005, 08:52 AM

In article <93hbgvg9o7sdlssthh7qtrq8gp23rk2uft@4ax.com>, willis_31_40
@yahoo.com says...[color=blue]
> Why does this work the way it does?
> If someone could explain return true, and return false to me I'd
> greatly appreciate it.
>[/color]

Or better yet...

function understand() {
return false;
}

--

Remove NOT from email address to reply. AntiSpam in action.

difference between return true; and return false;

Popular Articles

What is Bytes?