Why does document.write("...</script>") break my code? [duplicate]

Question

I'm trying to get the following Javascript work (it should be an embedded survey from formstack.com that shows up on specific days). However, when I try to view it all I get displayed is the string (without the quotes) "'); }" What is wrong?

<head>
<script type="text/javascript">

var theDate = new Date();
var dayOfWeek = theDate.getUTCDay();

// Returns true if the restaurant is open
function isOpen()
{
    //I'll fill this in later, for now, return true
    return true;
}
</script>

</head><body>
<script type = "text/javascript">
if(isOpen())
{
document.write('<script type="text/javascript" src="http://www.formstack.com/forms/js.php?1134414-uqmj2UXxEw-v2"></script>');
}
</script>
</body>

this does work, describe your problem... (What is the error, in what browser etc...) most of the time when you inject JS to the HTML you need to give it some time so the browser can interpret it.. — meo
– meo, Commented Nov 6, 2011 at 0:10

Guffa · Accepted Answer · 2011-11-06 00:10:46Z

2

Don't have a </script> tag in your string, that ends the script tag.

document.write('<scr'+'ipt type="text/javascript" src="http://www.formstack.com/forms/js.php?1134414-uqmj2UXxEw-v2"></scr'+'ipt>');

answered Nov 6, 2011 at 0:10

Guffa

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5 Comments

Jared Farrish Over a year ago

So why do you break up the <script part? I've known this method worked for some time, but haven't ever known why it works.

Guffa Over a year ago

@JaredFarrish: Just to be on the safe side. It works simply because </scr'+'ipt> is not interpreted as an ending tag for the script.

Jared Farrish Over a year ago

Just wondering... Why does JS interpret a script tag in a string as the ending tag for the calling statement? (Which is what I think you're saying, right?)

user166390 Over a year ago

@Guffa I believe it's the constucte </ that has to be guarded against, per spec, but this is likely guarded to only need to protect against </script> in modern browsers. <script> -- or generally, any < not in the form </ -- is perfectly fine/safe within a script block (for HTML).

Guffa Over a year ago

@JaredFarrish: Because the HTML tags are parsed before the script.

Šime Vidas · Accepted Answer · 2011-11-06 00:10:43Z

2

You can't have a string containing '</script>' inside a SCRIPT element. Consider loading additional scripts like so:

var script = document.createElement( 'script' );
script.src = 'http://www.formstack.com/forms/js.php?1134414-uqmj2UXxEw-v2';
document.body.appendChild( script );

Your preferred JavaScript library probably contains a dedicated function for this. For instance, I use jQuery, where it's done like so:

$.getScript( 'http://www.formstack.com/forms/js.php?1134414-uqmj2UXxEw-v2' );

answered Nov 6, 2011 at 0:10

Šime Vidas

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Comments

Jared Farrish · Accepted Answer · 2011-11-06 00:10:11Z

0

I've heard stories of javascript failing to execute inside document.write... try breaking it up:

document.write("script type = " + "text/javascript" + "src='http://www.formstack.com/forms/js.php?1134414-uqmj2UXxEw-v2'>" + "/script");

(greater and less than signs removed, you should know where to put them)

edited Nov 6, 2011 at 0:10

Jared Farrish

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answered Nov 6, 2011 at 0:09

Techboy6601

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1 Comment

Jared Farrish Over a year ago

"You should know where to put them" - Huh?

PackratDragon · Accepted Answer · 2011-11-06 01:26:42Z

-1

I wonder if the / of is being see as the escape character. Something that you can try is

String s = @"...." where .... is the text.

The @ tells the compiler to treat everything in "'s as a literal. I know that this works in both C# and Java. I am not 100% sure about javascript.

answered Nov 6, 2011 at 1:26

PackratDragon

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