JSFiddle - React, Tailwind, and code Playground

HTML

<form id="test">
    <input type="hidden" name="firstName" value="John">
    <input type="hidden" name="lastName" value="Doe">
</form>

JavaScript

console.log($("#test").serialize()); // firstName=John&lastName=Doe 

var data = $("#test").serializeArray();
console.log(data); // [Object, Object]

data.push({name: 'middleName', value: 'Bob'});
console.log(data); // Object, Object, Object]

console.log(data.serialize()); // Uncaught TypeError: undefined is not a function