Uncaught SyntaxError: Unexpected token ILLEGAL - A simple string syntactically wrong

Question

Why this seemingly simple string variable is syntactically wrong?

var str = "<script>functionName()</script>";

I am getting the following error

Uncaught SyntaxError: Unexpected token ILLEGAL

here is the fiddle

@Tushar I have tried this is in fiddle and in console. In console it works fine. In fiddle it gives this problem. I am trying to understand why it is happening. — gurvinder372, Dec 21 '15 at 12:55
The problem is explained by GokulShrinivas, it's because of `CDATA` added by fiddle — Tushar, Dec 21 '15 at 12:57

score 2 · Accepted Answer · answered Dec 21 '15 at 12:42

Open the console and try putting the string

var str = "<script>functionName()</script>";

There are no syntax errors and everything works fine.

When you are embedding the code in a script tag, like so

<script>
// code here
</script>

In JSFiddle, if you check the error you will see something like

<script type='text/javascript'>//<![CDATA[
window.onload=function(){
var str = "<script>functionName()</script>";
}//]]> 

</script>

The Browser does not allow </ characters in a string when you are embedding it in a <script> tag.

So, you'll need to escape it with a \

score 1 · Answer 2 · answered Dec 21 '15 at 12:27

1

This should work. Added a backslash "</script>".

<script>
    var str = "<script>functionName()<\/script>";
</script>

answered Dec 21 '15 at 12:27

Keyur Sakaria

The backslash is needed to escape the next character `/` – GokulSrinivas Dec 21 '15 at 12:28
1

@GokulSrinivas Try `"/s"` in console, not needed. – Tushar Dec 21 '15 at 12:29
This will help you understanding escaping forward slashes http://stackoverflow.com/questions/1580647/json-why-are-forward-slashes-escaped – Keyur Sakaria Dec 21 '15 at 12:30
@Tushar Please try the string `var str = "";` in the console too. You will not get any error. The problem comes when you try to embed it in a script tag. – GokulSrinivas Dec 21 '15 at 12:35

2 Answers2