const regex = /(?:[\(])*([\d]{3,3})(?:[\)\.\ ])*([\d]{3,3})(?:[\-\.])*([\d]{4,4})/g;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?:[\\(])*([\\d]{3,3})(?:[\\)\\.\\ ])*([\\d]{3,3})(?:[\\-\\.])*([\\d]{4,4})', 'g')
const str = `586.943.9341
5869439241
(586)123-4567
(586) 943-9341`;
const subst = `$1-$2-$3`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions