JSFiddle - React, Tailwind, and code Playground
JavaScript
var ssn = "1234567890";
var firstthree = ssn.substring(0,3);
var midtwo = ssn.substring(3,5);
var lastfour = ssn.substring(6,10);
var text = firstthree + "-" + midtwo + "-" + lastfour;
alert(text);