JSFiddle - React, Tailwind, and code Playground

JavaScript

var string = "title=Hello world&dropdown=on&count=on&hierarchical=on";
var stringArr = string.split("&");
console.log(stringArr);

var newObj = {};

for (var i = 0; i < stringArr.length; i++) {
    var parts = stringArr[i].split("=");
    newObj[parts[0]] = parts[1];
}

console.log(newObj);