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?

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?

• javascript
• regex

3 Answers 3

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__: /(?:)/

No need for a regular expression. Try this:

> patt1.source
"is"

I think what you need is this:

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