JSFiddle - React, Tailwind, and code Playground
JavaScript
String.prototype.splice = function( idx, rem, s ) {
return (this.slice(0,idx) + s + this.slice(idx + Math.abs(rem)));
};
var url = "www.domain.com/bla/?page=10";
var insertIndex = url.indexOf('page=10');
var final = url.splice( insertIndex, 0, "page=2&" ).replace('&page', '&show');
console.log(final);