Javascript .replace() / regex with code as string

Question

I'm trying to "remove" (just replace it with "") the following String:

<script type="text/javascript">
document.createElement("img").src="http://www.google.com"
</script>

From the following String:

<SCRIPT LANGUAGE=JavaScript>
var PAswf = "_ADPATH_[%SWF File%]";
var advurl = "_ADCLICK_";
var PAadvurl = escape(advurl);
var PAwidth = "[%Width%]";
var PAheight = "[%Height%]";
var wmValue = "_ADDCP(wm)_";
if (!wmValue)wmValue = "opaque";
var PAwmode = wmValue;
document.write('<OBJECT classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"');
document.write(' WIDTH="'+ PAwidth +'" HEIGHT="'+ PAheight +'">');
document.write('<PARAM NAME=movie VAL'+'UE="' + PAswf + '?clickTag='+ PAadvurl +'"><PARAM NAME=quality VALUE=high><PARAM NAME=wmode VALUE='+ PAwmode +'>');
document.write('<EMBED sr'+'c="'+PAswf + '?clickTag='+ PAadvurl +'" quality=high wmode='+ PAwmode);
document.write(' swLiveConnect=TRUE WIDTH="'+ PAwidth +'" HEIGHT="'+ PAheight +'"');
document.write(' TYPE="application/x-shockwave-flash">');
document.write('</EMBED></OBJECT>');
</SCRIPT>
<script type="text/javascript">
document.createElement("img").src="http://www.google.com"
</script>

As you can see, the String is at the bottom of the code block, but that shouldn't really matter. I've stored the first string as a variable, codeString, and tried the following.

// code refers to the bigger code string
code.replace(/codeString/gm, "");

Doesn't seem to match. I'm sure I'm doing something wildly wrong, but I've searched for about an hour and have come up empty. Any ideas?

Lekensteyn · Accepted Answer · 2011-09-13 14:42:30Z

up vote 5 down vote accepted

/codeString/ is a regular expression searching for the literal "codeString", not a variable containing a pattern. Also, string.replace(pattern, replacement) does not modify string but returns a new string with the replacement applied.

You do not need a regular expression for stripping fixed strings like this, the next code will remove the string once from code:

var codeString = '<script type="text/javascript">\n' +
    'document.createElement("img").src="http://www.google.com"\n' +
    '<\/script>';
code = code.replace(codeString, "");

edited Sep 13 '11 at 14:42

answered Sep 13 '11 at 14:35

Lekensteyn
16.5k12154

2

WARNING write '</script>' as '</sc'+'ript>' when you haven't defined a Doctype, combined with //<[CDATA[...//]]>, or your script will end too early. – Rob W Sep 13 '11 at 14:39

Ah, I forgot that the replace() doesn't actually modify the string. Needed to be re-assigned and it worked. Silly! :) – dmackerman Sep 13 '11 at 14:42

@Rob Good point, using <\/script> now. Note that it does not matter if the code was contained in an external js file. – Lekensteyn Sep 13 '11 at 14:43

Pointy · Answer 2 · 2011-09-13 14:35:55Z

up vote 1 down vote

Well you can start with

code.replace(codestring, "");

If it needs to be a regular expression, you can use:

code.replace(new RegExp(codestring, "gm"), "");

but be aware that the regex metacharacters should be escaped with backslashes.

answered Sep 13 '11 at 14:35

Pointy
125k12104187

In this particular case: (, ) and . --> \(, \) and \.. – Tim Pietzcker Sep 13 '11 at 14:37

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