Formatting dynamic regex expression

Question

Just curious. what are the differences between?

var a=text.replace(/(Nullam|ligula|in)/ig,'`<b>$1</b>`');

with

var string = "Nullam|lingula|in";  
var pattern = new RegExp (string, "ig");    
var a=text.replace(pattern ,'`<b>$1</b>`');

This should gives out the same result, but it doesn't. Any thoughts?

Thank you

If you wrote $0 instead of $1 in your second example, then you'd get the same result in both. Actually, you'd also get that if you used $0 in the first example. — Tim Pietzcker
– Tim Pietzcker, Commented Aug 1, 2011 at 20:15

Mrchief · Accepted Answer · 2011-08-01 20:07:34Z

3

You're missing parens in your later statement, so there are no captures. And the flag is gi, not ig (although I'm not sure if this makes any difference)

var reString = "(Nullam|lingula|in)"; var pattern = new RegExp (reString, "gi");

answered Aug 1, 2011 at 20:07

Mrchief

76.4k20 gold badges145 silver badges193 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Nebby Over a year ago

For example, when the first technique found one of words, it will make it bold, and wont' replace the word. Meanwhile, when the second one found one of words, it will make it bold and literally it will replace the word to "$1". That is what comes out from my experiment. What I am trying to achieve is to just make the word bold without literally replace the word. Is this possible? (with dynamic keywords)

Mrchief Over a year ago

Yes, and that's because you're missing the parens which creates a capture group.

Nebby Over a year ago

Following your suggestion. I tried and cannot get it to work. Here are my experiments: First technique jsfiddle.net/oceog/q8S7E AND Second technique: jsfiddle.net/UyWTf/1

Mrchief Over a year ago

You're not loading jQuery in the fiddle. This works in chrome: jsfiddle.net/UyWTf/2

Nebby Over a year ago

Interesting. It works in Chrome. Somehow after clearing all the caches and etc, it works now in Firefox. Anyway, I am still learning about RegExp. Thank you very much for your help. I really appreciate it.

Collectives™ on Stack Overflow

Formatting dynamic regex expression

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related