JSFiddle - React, Tailwind, and code Playground

JavaScript

var a = "emailID=a1%40a.comSEPmaths=0SEPphysics=1SEPchemistry=2SEPbotany=3SEPzoology=4SEPtamil=5SEPenglish=6SEPpolity=7SEPgk=8SEPhistory=9";
 
 var myarr = {};
var sep = "SEP";
 a.split(sep).forEach(function(item){
     var sepp = item.indexOf("=");
     myarr[item.substr(0,sepp)] = decodeURIComponent(item.substr(sepp+1));
 });
console.log(myarr);