How to replace text using regex with condition?

Question

I want to replace a link as plain text format to html format.

But I got the issue that, I don't know how to prepend the http:// prefix for the new replacement if in the original link does not exist.

var text        = "google.com and http://google.com";
var pattern     = /(\b((https?)\:\/\/)?[A-Za-z0-9]+\.(com|net|org))/ig;
text            = text.replace(pattern,"<a href='$1'>$1</a>");

I meant:

If: google.com will be replaced <a href="http://google.com">google.com</a>
If: http://google.com will be replaced <a href="http://google.com">http://google.com</a>

Just so you know.. www.google.com is not handled by your regex — parapura rajkumar
– parapura rajkumar, Commented Dec 28, 2011 at 4:21

Matt Ball · Accepted Answer · 2011-12-28 04:21:53Z

3

Use the overload of String.replace that takes a function:

var text = "google.com and http://google.com";
var pattern = /(\b((https?)\:\/\/)?[A-Za-z0-9]+\.(com|net|org))/ig;

text = text.replace(pattern, function (str, p1)
{
    var addScheme = p1.indexOf('http://') === -1
                    && p1.indexOf('https://') === -1;

    return '<a href="' + (addScheme ? 'http://' : '') + p1 + '">' + p1 + '</a>';
});

// text is:
// '<a href="http://google.com">google.com</a> and <a href="http://google.com">http://google.com</a>'

answered Dec 28, 2011 at 4:21

Matt Ball

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1 Comment

Matt Ball Over a year ago

And @parapura rajkumar is correct; the regex will not handle www.google.com (really, any subdomains), so you might want to fix that.

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