Caveats Encoding a C# string to a Javascript string

Question

I'm trying to write a custom Javascript MVC3 Helper class foe my project, and one of the methods is supposed to escape C# strings to Javascript strings.

I know C# strings are UTF-16 encoded, and Javascript strings also seem to be UTF-16. No problem here.

I know some characters like backslash, single quotes or double quotes must be backslash-escaped on Javascript so:

\ becomes \\
' becomes \'
" becomes \"

Is there any other caveat I must be aware of before writing my conversion method ?

EDIT: Great answers so far, I'm adding some references from the answers in the question to help others in the future.

Alex K. suggested using System.Web.HttpUtility.JavaScriptStringEncode, which I marked as the right answer for me, because I'm using .Net 4. But this function is not available to previous .Net versions, so I'm adding some other resources here:

CR  becomes \r   // Javascript string cannot be broke into more than 1 line
LF  becomes \n   // Javascript string cannot be broke into more than 1 line
TAB becomes \t

Control characters must be Hex-Escaped

JP Richardson gave an interesting link informing that Javascript uses UCS-2, which is a subset of UTF-16, but how to encode this correctly is an entirely new question.

LukeH on the comments below reminded the CR, LF and TAB chars, and that reminded me of the control chars (BEEP, NULL, ACK, etc...).

Don't forget to encode newlines, tabs and any other special chars. JavaScriptStringEncode, as suggested by Alex, will handle that for you. — LukeH
– LukeH, Commented Feb 23, 2012 at 13:19

Alex K. · Accepted Answer · 2012-02-23 13:05:22Z

35

(.net 4) You can;

System.Web.HttpUtility.JavaScriptStringEncode(@"aa\bb ""cc"" dd\tee", true);
== 
"aa\\bb \"cc\" dd\\tee"

answered Feb 23, 2012 at 13:05

Alex K.

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3 Comments

Machado Over a year ago

Nice! I'm using MVC3 with .Net 4, so this is very useful!

Matt R Over a year ago

What's the solution for users of .net version < 4?

Dai Over a year ago

Handily, this also works in .NET Core and .NET 5+, despite being in the System.Web namespace. Since .NET Core, this just forwards JavaScriptStringEncode to System.Text.Encodings.Web btw.

JP Richardson · Accepted Answer · 2012-02-23 14:20:08Z

1

It's my understanding that you do have to be careful, as JavaScript is not UTF-16, rather, it's UCS-2 which I believe is a subset of UTF-16. What this means for you, is that any character that is represented than a higher code point of 2 bytes (0xFFFF) could give you problems in JavaScript.

In summary, under the covers, the engine may use UTF-16, but it only exposes UCS-2 like methods.

Great article on the issue: http://mathiasbynens.be/notes/javascript-encoding

answered Feb 23, 2012 at 14:20

JP Richardson

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1 Comment

Machado Over a year ago

So, how could we safely transform the C# UTF-16 into UCS-2 in order to encode the string the right way ?

Chris Gessler · Accepted Answer · 2012-02-23 12:57:12Z

0

Just use Microsoft.JScript.GlobalObject.escape

Found it here: http://forums.asp.net/p/1308104/4468088.aspx/1?Re+C+equivalent+of+JavaScript+escape+

answered Feb 23, 2012 at 12:57

Chris Gessler

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Comments

Allan Pereira · Accepted Answer · 2016-10-21 17:27:44Z

0

Instead of using JavaScriptStringEncode() method, you can encode server side using:

HttpUtility.UrlEncode()

When you need to read the encoded string client side, you have to call unescape() javascript function before using the string.

edited Oct 21, 2016 at 17:27

Allan Pereira

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answered Jul 15, 2013 at 9:47

bre_dev

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2 Comments

Casey Over a year ago

Why would you choose to do it this way?

user746461 Over a year ago

My string is not url, why do I use UrlEncode. It seems silly. But I believe it will work.

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