Dynamically assigning a Regex pattern in Javascript -

how dynamically assign pattern?

i've tried:

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

but code produces error:

uncaught typeerror: cannot read property 'length' of null

i've tried use pattern "/b/g" doesn't work

you should this:

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

so, this:

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

read more @ mdn

update:

if want in way, can do:

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