Number Validator

hello good afternoon, I am in this part of the project where we have to validate a US phone number, try to make all the regular expression in 1 (it did not go well) so I tried to decide between the numbers that start with 1 and those that do not . but I still have a problem with this case (I know how to solve that particular case but another one would fail)
telephoneCheck(“1 555)555-5555”)` should return false.

I am thankful for any kind of help

function telephoneCheck(str) {

var regex1= /^([1])/


  var regex2 = /^([1])\s*\(*[0-9]{3}\)*\-*\s*[0-9]{3}\)*\-*\s*[0-9]{4}$/


  return regex2.test(str)

}else if(regex1.test(str)===false){

var myRegex=  /^(\([0-9]{3}\)|[0-9]{3})\s*\(*\-*[0-9]{3}\)*\-*\s*[0-9]{4}$/

return myRegex.test(str) 



console.log(telephoneCheck("1 555)555-5555"));

You can make any preceding character or group optional by adding ?

const re = /1?\d\d\d/;

re.test('1555'); // true
re.test('555'); // true

thanks, changed everything back to 1 only regex thanks to that and it work.