JSFiddle - React, Tailwind, and code Playground

JavaScript

str = 'a=6&id=99';
var arr = str.split('&');
var obj = {};
for(var i = 0; i < arr.length; i++) {
    var bits = arr[i].split('=');
    obj[bits[0]] = bits[1];
}
//alert(obj.a);
//alert(obj.id);
str = '';
for(key in obj) {
    str += key + '=' + obj[key] + '&';
}
str = str.slice(0,str.length - 1); 
alert(str);