unterminated regular expression literal js error

Question

I have added jQuery validator add method for the presence of http check in url field.

JS

jQuery.validator.addMethod("valid_url", function(value, element) {
 if(!/^(https?|ftp):\/\/i.test(val))
    val = 'http://'+val; // set both the value
    $(elem).val(val); // also update the form element
 }

My Console throws
"unterminated regular expression literal" error in the following line.

if(!/^(https?|ftp):\/\/i.test(val))

What my mistake is?

Answer 1

Regular expression literals should be surrounded by the delimiters(/). There's no terminating delimiter:

/^(https?|ftp):\/\//i
//                 ^

---

For example:

>> /^(https?|ftp):\/\//i.test('http://stackoverflow.com/')
true
>> /^(https?|ftp):\/\//i.test('telnet://stackoverflow.com/')
false

Answer 2

You can also get this error if you're simply attempting to concatenate a variable that utilizes a regular expression and forget a quotation mark somewhere.