clean_up_regex

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(S) {
    // write your code in JavaScript (Node.js 6.4.0)
    var numericString =  S.trim;
    var finalString = '';
    //lets remove all the non numeric characters in the string
    numericString = S.replace(/\s|-/g, '');
    //we removed the chuff ensure we have more than 2 characters
    
    //watch our edge cases 
    //this can be made skinnier and more perfomant 
    while(numericString.length > 0) {
        if(numericString.length <= 2) {
            finalString += `${numericString.substr(0,2)}`; 
            break;
        }
        if(numericString.length <= 3) {
            finalString += `${numericString.substr(0,3)}`; 
            break;
        }
        if(numericString.length == 4) {
            finalString += `${numericString.substr(0,2)}-`; 
            numericString = numericString.replace(/^.{0,2}/, '');
            finalString += `${numericString.substr(0,2)}`
            break;
        }
        finalString += `${numericString.substr(0,3)}-`; 
        numericString = numericString.replace(/^.{0,3}/, '');   
    }
    return finalString;
}