JAVASCRIPT

javascript masking if input matches patter

document.getElementById("phone").addEventListener("keyup", function(){
    // restart the match
    this.value = this.value.replace(/s/g, "");
    // Assess the amount needed
    var v = this.value.match(/(d)(d{1,3})?(d{1,2})?(d+)?/);
    if(v){
      // Save the desired value depending on its existence
      v =  (v[1]?v[1]+(v[2]?" "+v[2]+(v[3]?" "+v[3]+(v[4]?" "+v[4]:""):""):""):"");
      // and yea!
      this.value = v;
    }
});