How do I do run a regex on a regex in javascript?

Question

I have the following regex pattern and string:

var str="Is this all there is?";
var patt1=/is/gi;

I would like to just extract the main expression is (without the modifiers) from var patt1 using another regular expression, which we can call var patt2 for arguments sake.

How is this possible to do in vanilla JavaScript?

xdazz · Accepted Answer · 2012-12-25 00:55:08Z

11

Yes, patt1 is a regex object.

You could get the regex source by patt1.source.

> console.dir(patt1);
  /is/gi
    global: true
    ignoreCase: true
    lastIndex: 0
    multiline: false
    source: "is"
    __proto__: /(?:)/

answered Dec 25, 2012 at 0:55

xdazz

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1 Comment

technojas Over a year ago

+1 - Accepting this answer only because I saw it first - otherwise there was not much difference between them two :)

Mark Byers · Accepted Answer · 2012-12-25 00:55:17Z

9

No need for a regular expression. Try this:

> patt1.source
"is"

answered Dec 25, 2012 at 0:55

Mark Byers

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1 Comment

technojas Over a year ago

+1 - Wow! I had no idea this method existed on the regex object.

pigletfly · Accepted Answer · 2012-12-25 01:20:42Z

0

I think what you need is this:

 var patt1=/[is]/gi;
 alert(patt1.test());

answered Dec 25, 2012 at 1:20

pigletfly

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