How to Add Constraint With No Validation?

Composing Regex doesn't work (JS regular expressions)

Harris

I'm trying to compose a regex the following way, but I am getting an error VM114:5 Uncaught SyntaxError: Invalid regular expression: /d+(?:/d+)+(?:+d+(?:/d+)+)*(?:,d+(?:/d+)+(?:+d+(?:/d+)+)*)*/: Nothing to repeat

 const r = "d+(?:/d+)+"
    const r2 = `${r}(?:+${r})*`
    const r3 = `${r2}(?:,${r2})*`

new RegExp(r3)

Anyone know how to avoid this?