replace javascript regexp matched group with a dollar sign

Question

This one should be pretty simple :

Let's take the string : str="1.99 or 4.89"

I want to add a dollar sign in front of the amounts.

I tried :

str.replace(/(\d\.\d\d)/g,"$$1"));

it gives me : "$1 or $1"...

So I'm stuck with doing :

str.replace(/(\d\.\d\d)/g,"$ $1").replace(/\$ /g,'$')

It works but I'm sure there's a better way! I've tried escaping both $ signs, and a few other things... Looking forward to your answers :)

Answer 1

"1.99 or 4.89".replace(/(\d\.\d\d)/g, "$$$1")
// => "$1.99 or $4.89"

Since $ is special in replacement string, it must be escaped into $$ for a literal $. It is not escaped using the \ character, which is a general string escape mechanism, and processed before the string reaches replace (i.e. if you say "\$", it becomes "$" before being passed as an argument, so replace never sees the escaping).