matching regex pattern in javascript using RegExp

I have a string from which I want to check if it only contains characters that are allowed. I want only characters of

• alphanumeric (lower & upper) : A-Z, a-z

• numeric (0-9)

• special characters: _&!.-

• space

example of valid strings:

• title1 - header
• title2&&& header_!.
• 09
• a912
• ...dd

example of invalid strings

• a$$$ ()
• a12345^&6**

if at least one of characters is not in the special characters so it not valid string. I would like to know how do test it in javascript. the regex patterns come from server so it string. I convert the regex pattern string by using RegExp but all of them show false, even some of them are valid. the three first lines should be valid (true)

 const pattern = "^[a-z0-9_&!.-\\s]+$";

                const strings = [
                  `title1 - header`,
                  `title2&&& header_!.-`,
                  `09`,
                  `a912 dd`,
                  `a$$$ ()`,
                  `a12345^&6**`
                ]
                const regex = new RegExp(pattern);

                strings.forEach(str => {

                  console.log(str, ' ---> ', regex.test(str));
                });