SyntaxError: Invalid regular expression:

Question

I'm pretty sure my regex is correct, but anytime I try to test the code, I get an invalid regular expression error with a nothing to repeat at the end.

I'll attach the code below

 function checkPhoneNumber(phoneNumber) {

    let phoneNumberValidation = RegExp("(\+1[ ]?)((\(?[0-9]{3}\)?[-\. ]?))([0-9]{3}[-\. ]?)([0-9]{4})");
    if (phoneNumberValidation.test(phoneNumber)) {
        return true;
    } else {
        return false;
    }

}