JSFiddle - React, Tailwind, and code Playground

JavaScript

var search = "?er=78&fgf=656&fg=67"

    key = "er";
    var value = search .match(new RegExp(key + "=(.*?)($|\&)", "i"))[1];
document.write(value + "  ");

  key = "fgf";
    var value = search .match(new RegExp(key + "=(.*?)($|\&)", "i"))[1];
document.write(value + "  ");
  key = "fg";
    var value = search .match(new RegExp(key + "=(.*?)($|\&)", "i"))[1];
document.write(value + "  ");