JSFiddle - React, Tailwind, and code Playground

JavaScript

// Our string URL
var urlString = "http://crm//WebResources/abaxis_popup?Data=recordid%3dElectrolyte%26sometext%3daw_device%26somemoretext%3dpolyclinic";

// Replace the HTML chars to the regular text chars. 
urlString = urlString.replace(/Data=/g, '');

urlString = urlString.replace(/%26/g, '?');
urlString = urlString.replace(/%3d/g, '=');

// Create a function to parse the params and values 
function transformToAssocArray( prmstr ) {
    var params = {};
    var prmarr = prmstr.split("&");
    for ( var i = 0; i < prmarr.length; i++) {
        var tmparr = prmarr[i].split("=");
        params[tmparr[0]] = tmparr[1];
    }
    return params;
}

// Use it. 
var result = transformToAssocArray(urlString);

console.log(urlString);