unable to test regex in javascript

Question

I'm pretty unfamiliar with RegExp, and Im trying to implement it to detect urls in strings. The one regexp I want to use is this one (please don't provide your own):

/(((http|ftp|https)://)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:/~+#-]*[\w@?^=%&amp;/~+#-])?)/g

And replace all the matches with this:

<a href="$1">$1</a>

If you visit http://gskinner.com/RegExr/ with that example and use it in the replace, you'll see it works flawlessly, but it's impossible to build a working solution with this in javascript.

var text = "hi, demo link http://stackoverflow.com is a great website"
//regexp magic


//expected result:
textWithLink ="hi, demo link <a href="http://stackoverflow.com">http://stackoverflow.com</a> is a great website"

How have you tried to express that regex in JS syntax? How have you tried to use the resulting regex object? — Quentin
– Quentin, Commented Feb 26, 2013 at 15:22
@Jack you have to escape the forward slashes within the regex — John Dvorak
– John Dvorak, Commented Feb 26, 2013 at 15:24
@JanDvorak Hmm, I assumed that wasn't necessary when you do var re = new RegExp('(((http|ftp|https)://)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&:/~+#-]*[\w@?^=%&/~+#-])?)', 'g'); — Ja͢ck
– Ja͢ck, Commented Feb 26, 2013 at 15:29
@Jack that's correct, but you normally create regexes as /.../g — John Dvorak
– John Dvorak, Commented Feb 26, 2013 at 15:31
@JanDvorak That's just an alternative writing style, I don't think that should really matter, except for the fact that you have to escape the forward slash when the delimiter is already that. — Ja͢ck
– Ja͢ck, Commented Feb 26, 2013 at 15:32

Seimen · Accepted Answer · 2013-02-26 15:31:55Z

2

var str = 'hi, demo link http://stackoverflow.com is a great website',
    regex = /(((http|ftp|https):\/\/)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:\/~+#-]*[\w@?^=%&amp;\/~+#-])?)/g;
str.replace(regex, '<a href="$1">$1</a>');

Note: It's your exact regex, I just escaped the forward slashes.

answered Feb 26, 2013 at 15:31

Seimen

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monxas Over a year ago

Thanks to all, I now understand much better how to use regex in js. Awesome!

Denys Séguret · Accepted Answer · 2013-02-26 15:22:38Z

1

You can do this

var ok = /(((http|ftp|https):\/\/)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:/~+#-]*[\w@?^=%&amp;/~+#-])?)/.test(str);

to test if a string is an URL.

If you want to look for URLs in a string, use

var matches = str.match(/(((http|ftp|https):\/\/)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:/~+#-]*[\w@?^=%&amp;/~+#-])?)/g);

Note that it's a regex literal and that I had to escape the /.

answered Feb 26, 2013 at 15:22

Denys Séguret

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1 Comment

11684 Over a year ago

@JanDvorak I already answered my own question, I'll delete my comments.

Álvaro González · Accepted Answer · 2013-02-26 15:29:49Z

1

The RegExp literal you provide is invalid:

/(((http|ftp|https)://)?[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:/~+#-]*[\w@?^=%&amp;/~+#-])?)/g
^                   ^^
Start               |\__ Error
                    |
                   End

It works in the link you provide because that application strips delimiters automatically and inadvertently fixes the error.

answered Feb 26, 2013 at 15:29

Álvaro González

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