Word boundary won't match the beginning or end in Javascript

Question

I'm getting unexpected results with this code:

'foo'.match(new RegExp('\bfoo\b')); // Returns null

Why is this returning null while this one returns "foo"?

'foo'.match(new RegExp('foo')); // Returns "foo"

Doesn't a word boundary marker match the beginning and end as well?

EDIT: I need the regular expression itself to be a string because I am injecting variables into it.

Turaco

Answer 1

Escape the backslashes

'foo'.match(new RegExp('\\bfoo\\b'));

Po

Do you know why the backslash for this needs to be escaped but it doesn't for something like getting a forward slash – Estabrook

Answer 2

Don't wrap it in quotes... instead, do this:-

'foo'.match(new RegExp(/\bfoo\b/))

Keelboat

I need it to be a string because I'm dropping in values. – Turaco

@mattalexx: That really should be part of your question if you want it to persist here and be useful to others. – Eagre