// Assuming "?order=1&total=30"

var urlParams = new URLSearchParams(window.location.search);

console.log(urlParams.has('order')); // true
console.log(urlParams.get('order')); // "order"
console.log(urlParams.getAll('order')); // ["order"]
console.log(urlParams.toString()); // "order=1&total=30""
console.log(urlParams.append('currency', 'usd')); // "?order=1&total=30&active=usd"

URLSearchParams also provides familiar Object methods like keys(), values(), and entries():

var keys = urlParams.keys();
for(key of keys) {
console.log(key);
}
// post
// action

var entries = urlParams.entries();
for(pair of entries) {
console.log(pair[0], pair[1]);
}

Javascript fallback

While URLSearchParams is ideal, not all browsers support that API. There's a polyfill available but if you want a tiny function for basic query string parsing, the following is a function stolen from the A-Frame VR toolkit which parses the query string to get the key's value you'd like:

function getUrlParameter(name) {
name = name.replace(/[\[]/, '\\[').replace(/[\]]/, '\\]');
var regex = new RegExp('[\\?&]' + name + '=([^&#]*)');
var results = regex.exec(location.search);
return results === null ? '' : decodeURIComponent(results[1].replace(/\+/g, ' '));
};

With the function above, you can get individual parameter values:

getUrlParameter('order'); // "1"