A function that returns true if the passed string looks like a valid US phone number.

telephone-number-validator.js

function telephoneCheck(str) {
  if(!parenthesesBalanced(str)){
    return false;
  }
  const regex = /^1?\s*(\(?\d{3}\)?[-]?\s*){2}\d{4}$/
  return regex.test(str);
}

function parenthesesBalanced(str){
  const openBracketRegex = /\(/g
  const closeBracketRegex = /\)/g
  let result1 = str.match(openBracketRegex)
  let result2 = str.match(closeBracketRegex)

  if(!result1){
    result1 = []
  }

  if(!result2){
    result2 = []
  }
  return result1.length == result2.length
}

telephoneCheck("555-555-5555");