Dynamically assigning a Regex pattern in Javascript

Question

How do I dynamically Assign a pattern?

I've tried:

var str = "hebbbbllo";
var patt = new RegExp;
patt =("b", "g");
console.log(str.match(patt).length);

But the code produces an error:

Uncaught TypeError: Cannot read property 'length' of null

I've also tried to use the pattern "/b/g" but it also doesn't work

Amit Joki · Accepted Answer · 2014-04-20 09:53:46Z

2

You should do this:

var patt = new RegExp("pattern","flags");

So, do this:

var str = "hebbbbllo";
var patt = new RegExp("b","g");
console.log(str.match(patt).length);

Update:

If you want to do it in your way, you can do:

var str = "hebbbbllo";
var patt = RegExp;
var regex = patt("b", "g");    
console.log(str.match(regex).length);

answered Apr 20, 2014 at 9:48

Amit Joki

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but i said i want to assign it dynamically, after i'm declaring the variable